diff --git a/.github/workflows/android.yml b/.github/workflows/android.yml
index b15871c789..a62c9b5e4d 100644
--- a/.github/workflows/android.yml
+++ b/.github/workflows/android.yml
@@ -92,18 +92,18 @@ jobs:
         id: cache_ndk
         uses: actions/cache@v2
         with:
-          path: /tmp/android-ndk-r16b
-          key: android-ndk-${{ matrix.os }}-r16b
+          path: /tmp/android-ndk-r21e
+          key: android-ndk-${{ matrix.os }}-r21e
 
       - name: Check cached NDK
         shell: bash
         if: steps.cache_ndk.outputs.cache-hit != 'true'
         run: |
           # If the NDK failed to download from the cache, but there is a
-          # /tmp/android-ndk-r16b directory, it's incomplete, so remove it.
-          if [[ -d "/tmp/android-ndk-r16b" ]]; then
+          # /tmp/android-ndk-r21e directory, it's incomplete, so remove it.
+          if [[ -d "/tmp/android-ndk-r21e" ]]; then
             echo "Removing incomplete download of NDK"
-            rm -rf /tmp/android-ndk-r16b
+            rm -rf /tmp/android-ndk-r21e
           fi
 
       - name: Update homebrew (avoid bintray errors)
diff --git a/.github/workflows/cpp-packaging.yml b/.github/workflows/cpp-packaging.yml
index 48604ecbee..8ef02e6dae 100644
--- a/.github/workflows/cpp-packaging.yml
+++ b/.github/workflows/cpp-packaging.yml
@@ -237,13 +237,11 @@ jobs:
           path: firebase-cpp-sdk-ios-tvos-package.tgz
 
   build_and_package_android:
-    name: build-and-package-android-${{matrix.stl}}
+    name: build-and-package-android
     runs-on: ubuntu-latest
     if: ${{ github.event.inputs.downloadPublicVersion == '' && github.event.inputs.downloadPreviousRun == '' }}
     strategy:
       fail-fast: false
-      matrix:
-        stl: ["c++", "gnustl"]
     steps:
       - name: fetch SDK
         uses: actions/checkout@v2.3.1
@@ -261,18 +259,18 @@ jobs:
         id: cache_ndk
         uses: actions/cache@v2
         with:
-          path: /tmp/android-ndk-r16b
-          key: android-ndk-${{ matrix.os }}-r16b
+          path: /tmp/android-ndk-r21e
+          key: android-ndk-${{ runner.os }}-r21e
 
       - name: install prerequisites
         run: sdk-src/build_scripts/android/install_prereqs.sh
 
       - name: build sdk
         run: |
-          sdk-src/build_scripts/android/build.sh firebase-cpp-sdk-android-${{ matrix.stl }}-build sdk-src ${{ matrix.stl }}
-          sdk-src/build_scripts/android/package.sh firebase-cpp-sdk-android-${{ matrix.stl }}-build firebase-cpp-sdk-android-${{ matrix.stl }}-package ${{ matrix.stl }}
-          cd firebase-cpp-sdk-android-${{ matrix.stl }}-package
-          tar -czhf ../firebase-cpp-sdk-android-${{ matrix.stl}}-package.tgz .
+          sdk-src/build_scripts/android/build.sh firebase-cpp-sdk-android-build sdk-src
+          sdk-src/build_scripts/android/package.sh firebase-cpp-sdk-android-build firebase-cpp-sdk-android-package
+          cd firebase-cpp-sdk-android-package
+          tar -czhf ../firebase-cpp-sdk-android-package.tgz .
 
       - name: Print built libraries
         shell: bash
@@ -292,8 +290,8 @@ jobs:
       - name: upload artifacts
         uses: actions/upload-artifact@v2.2.2
         with:
-          name: firebase-cpp-sdk-android-${{ matrix.stl }}-package
-          path: firebase-cpp-sdk-android-${{ matrix.stl }}-package.tgz
+          name: firebase-cpp-sdk-android-package
+          path: firebase-cpp-sdk-android-package.tgz
 
   build_desktop:
     name: build-${{ matrix.sdk_platform }}-${{ matrix.architecture }}-${{ matrix.build_type }}-${{ matrix.msvc_runtime }}-${{ matrix.linux_abi }}
diff --git a/.github/workflows/integration_tests.yml b/.github/workflows/integration_tests.yml
index 32cbe45d42..75991e4700 100644
--- a/.github/workflows/integration_tests.yml
+++ b/.github/workflows/integration_tests.yml
@@ -433,8 +433,8 @@ jobs:
         id: cache_ndk
         uses: actions/cache@v2
         with:
-          path: /tmp/android-ndk-r16b
-          key: android-ndk-${{ matrix.os }}-r16b
+          path: /tmp/android-ndk-r21e
+          key: android-ndk-${{ matrix.os }}-r21e
       - name: Setup python
         uses: actions/setup-python@v2
         with:
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5d3410f251..cb610fdc90 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -81,11 +81,6 @@ option(FIREBASE_GITHUB_ACTION_BUILD
 option(FIREBASE_QUICK_TEST
        "Enable quick tests will skip tests which requires access to the SECRET" OFF)
 
-set(FIREBASE_ANDROID_STL "" CACHE STRING "STL implementation to use.")
-if (NOT FIREBASE_ANDROID_STL STREQUAL "")
-  set(ANDROID_STL ${FIREBASE_ANDROID_STL})
-endif()
-
 set(FIREBASE_PYTHON_EXECUTABLE "python" CACHE FILEPATH
   "The Python interpreter to use, such as one from a venv")
 
diff --git a/admob/build.gradle b/admob/build.gradle
index 6b54fd5f33..f1b5a00c52 100644
--- a/admob/build.gradle
+++ b/admob/build.gradle
@@ -30,11 +30,6 @@ allprojects {
 
 apply plugin: 'com.android.library'
 
-ext {
-  firebaseAndroidStl = System.getenv('FIREBASE_ANDROID_STL')
-  firebaseAndroidStl = firebaseAndroidStl != null ? firebaseAndroidStl : ''
-}
-
 android {
   compileSdkVersion 28
   buildToolsVersion '28.0.3'
@@ -71,8 +66,7 @@ android {
         //           Only include needed project.
         arguments '-DFIREBASE_CPP_USE_PRIOR_GRADLE_BUILD=ON',
                 '-DFIREBASE_INCLUDE_LIBRARY_DEFAULT=OFF',
-                '-DFIREBASE_INCLUDE_ADMOB=ON',
-		"-DFIREBASE_ANDROID_STL=${firebaseAndroidStl}"
+                '-DFIREBASE_INCLUDE_ADMOB=ON'
 	}
     }
   }
diff --git a/analytics/build.gradle b/analytics/build.gradle
index 9395803986..b10304768b 100644
--- a/analytics/build.gradle
+++ b/analytics/build.gradle
@@ -30,11 +30,6 @@ allprojects {
 
 apply plugin: 'com.android.library'
 
-ext {
-  firebaseAndroidStl = System.getenv('FIREBASE_ANDROID_STL')
-  firebaseAndroidStl = firebaseAndroidStl != null ? firebaseAndroidStl : ''
-}
-
 android {
   compileSdkVersion 28
   buildToolsVersion '28.0.3'
@@ -71,8 +66,7 @@ android {
         //           Only include needed project.
         arguments '-DFIREBASE_CPP_USE_PRIOR_GRADLE_BUILD=ON',
                 '-DFIREBASE_INCLUDE_LIBRARY_DEFAULT=OFF',
-                '-DFIREBASE_INCLUDE_ANALYTICS=ON',
-		"-DFIREBASE_ANDROID_STL=${firebaseAndroidStl}"
+                '-DFIREBASE_INCLUDE_ANALYTICS=ON'
       }
     }
   }
diff --git a/app/build.gradle b/app/build.gradle
index 9ed5f73643..89edc14b32 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -30,11 +30,6 @@ allprojects {
 
 apply plugin: 'com.android.library'
 
-ext {
-  firebaseAndroidStl = System.getenv('FIREBASE_ANDROID_STL')
-  firebaseAndroidStl = firebaseAndroidStl != null ? firebaseAndroidStl : ''
-}
-
 android {
   compileSdkVersion 28
   buildToolsVersion '28.0.3'
@@ -67,8 +62,7 @@ android {
       cmake {
         targets 'firebase_app'
         // Don't configure all the cmake subprojects.
-        arguments '-DFIREBASE_INCLUDE_LIBRARY_DEFAULT=OFF',
-		  "-DFIREBASE_ANDROID_STL=${firebaseAndroidStl}"
+        arguments '-DFIREBASE_INCLUDE_LIBRARY_DEFAULT=OFF'
       }
     }
   }
diff --git a/app/src/include/firebase/app.h b/app/src/include/firebase/app.h
index 1758703391..6b81bc42ed 100644
--- a/app/src/include/firebase/app.h
+++ b/app/src/include/firebase/app.h
@@ -50,11 +50,6 @@ namespace internal {
 class AppInternal;
 }  // namespace internal
 
-#if FIREBASE_PLATFORM_ANDROID && defined(__GLIBCXX__)
-#warning \
-    "Firebase support for gnustl is deprecated and will be removed in the next major release. Please use libc++ instead."
-#endif
-
 /// @brief Reports whether a Firebase module initialized successfully.
 enum InitResult {
   /// The given library was successfully initialized.
diff --git a/auth/build.gradle b/auth/build.gradle
index 831c181747..1874f97383 100644
--- a/auth/build.gradle
+++ b/auth/build.gradle
@@ -30,11 +30,6 @@ allprojects {
 
 apply plugin: 'com.android.library'
 
-ext {
-  firebaseAndroidStl = System.getenv('FIREBASE_ANDROID_STL')
-  firebaseAndroidStl = firebaseAndroidStl != null ? firebaseAndroidStl : ''
-}
-
 android {
   compileSdkVersion 28
   buildToolsVersion '28.0.3'
@@ -71,8 +66,7 @@ android {
         //           Only include needed project.
         arguments '-DFIREBASE_CPP_USE_PRIOR_GRADLE_BUILD=ON',
                 '-DFIREBASE_INCLUDE_LIBRARY_DEFAULT=OFF',
-                '-DFIREBASE_INCLUDE_AUTH=ON',
-		"-DFIREBASE_ANDROID_STL=${firebaseAndroidStl}"
+                '-DFIREBASE_INCLUDE_AUTH=ON'
       }
     }
   }
diff --git a/build_scripts/android/build.sh b/build_scripts/android/build.sh
index f2373e3ea9..16e4d456ab 100755
--- a/build_scripts/android/build.sh
+++ b/build_scripts/android/build.sh
@@ -4,10 +4,9 @@
 
 buildpath=$1
 sourcepath=$2
-stl=$3
 
 if [[ -z "${buildpath}" || -z "${sourcepath}" ]]; then
-    echo "Usage: $0 <build path> <source path> [c++|gnustl]"
+    echo "Usage: $0 <build path> <source path> [c++]"
     exit 1
 fi
 
@@ -16,14 +15,6 @@ if [[ ! -d "${sourcepath}" ]]; then
     exit 2
 fi
 
-if [[ "${stl}" == "c++" || "${stl}" == "gnustl" ]]; then
-    export FIREBASE_ANDROID_STL="${stl}"_static
-elif [[ ! -z "${stl}" ]]; then
-    echo "Invalid STL specified."
-    echo "Valid STLs are: 'c++' (default) or 'gnustl'"
-    exit 2
-fi
-
 origpath=$( pwd -P )
 
 mkdir -p "${buildpath}"
@@ -36,21 +27,15 @@ absbuildpath=$( pwd -P )
 cd "${origpath}"
 
 # If NDK_ROOT is not set or is the wrong version, use to the version in /tmp.
-if [[ -z "${NDK_ROOT}" || ! $(grep -q "Pkg\.Revision = 16\." "${NDK_ROOT}/source.properties") ]]; then
-    if [[ ! -d /tmp/android-ndk-r16b ]]; then
-	echo "Recommended NDK version r16b not present in /tmp."
-	if [[ ! -z "${stl}" ]]; then
-	    echo "STL may only be specified if using the recommended NDK version."
-	    echo "Please run install_prereqs.sh script and try again."
-	    exit 2
-	else
-	    echo "Please run install_prereqs.sh if you wish to use the recommended NDK version."
-	    echo "Continuing with default NDK..."
-	    sleep 2
-	fi
+if [[ -z "${NDK_ROOT}" || ! $(grep -q "Pkg\.Revision = 21\." "${NDK_ROOT}/source.properties") ]]; then
+    if [[ ! -d /tmp/android-ndk-r21e ]]; then
+        echo "Recommended NDK version r21e not present in /tmp."
+        echo "Please run install_prereqs.sh if you wish to use the recommended NDK version."
+        echo "Continuing with default NDK..."
+        sleep 2
     fi
-    export NDK_ROOT=/tmp/android-ndk-r16b
-    export ANDROID_NDK_HOME=/tmp/android-ndk-r16b
+    export NDK_ROOT=/tmp/android-ndk-r21e
+    export ANDROID_NDK_HOME=/tmp/android-ndk-r21e
 fi
 cd "${sourcepath}"
 set +e
@@ -72,16 +57,16 @@ set -e
 declare -a paths
 for lib in *; do
     if [[ -d "${lib}/build" ]]; then
-	paths+=("${lib}/build")
+        paths+=("${lib}/build")
     fi
     if [[ -d "${lib}/.externalNativeBuild" ]]; then
-	paths+=("${lib}/.externalNativeBuild")
+        paths+=("${lib}/.externalNativeBuild")
     fi
     if [[ -d "${lib}/${lib}_resources/build" ]]; then
-	paths+=("${lib}/${lib}_resources/build")
+        paths+=("${lib}/${lib}_resources/build")
     fi
     if [[ -d "${lib}/${lib}_java/build" ]]; then
-	paths+=("${lib}/${lib}_java/build")
+        paths+=("${lib}/${lib}_java/build")
     fi
 done
 set -x
diff --git a/build_scripts/android/install_prereqs.sh b/build_scripts/android/install_prereqs.sh
index ffc601da2d..6bb0f19d7e 100755
--- a/build_scripts/android/install_prereqs.sh
+++ b/build_scripts/android/install_prereqs.sh
@@ -21,11 +21,11 @@ else
     # Retry up to 10 times because Curl has a tendency to timeout on
     # Github runners.
     for retry in {1..10} error; do
-	if [[ $retry == "error" ]]; then exit 5; fi
-	curl -LSs \
+        if [[ $retry == "error" ]]; then exit 5; fi
+        curl -LSs \
              "https://download.sysinternals.com/files/Strings.zip" \
              --output Strings.zip && break
-	sleep 300
+        sleep 300
     done
     set -e
     unzip -q Strings.zip && rm -f Strings.zip
@@ -60,29 +60,29 @@ if [[ -z "${ANDROID_HOME}" ]]; then
     exit 1
 fi
 
-if [[ -z "${NDK_ROOT}" || -z $(grep "Pkg\.Revision = 16\." "${NDK_ROOT}/source.properties") ]]; then
-    if [[ -d /tmp/android-ndk-r16b && \
-	      -n $(grep "Pkg\.Revision = 16\." "/tmp/android-ndk-r16b/source.properties") ]]; then
-	    echo "Using NDK r16b in /tmp/android-ndk-r16b".
+if [[ -z "${NDK_ROOT}" || -z $(grep "Pkg\.Revision = 21\." "${NDK_ROOT}/source.properties") ]]; then
+    if [[ -d /tmp/android-ndk-r21e && \
+              -n $(grep "Pkg\.Revision = 21\." "/tmp/android-ndk-r21e/source.properties") ]]; then
+            echo "Using NDK r21e in /tmp/android-ndk-r21e".
     else
         echo "NDK_ROOT environment variable is not set, or NDK version is incorrect."
-        echo "This build requires NDK r16b for STLPort compatibility, downloading..."
-	    if [[ -z $(which curl) ]]; then
-	        echo "Error, could not run 'curl' to download NDK. Is it in your PATH?"
-	        exit 1
-	    fi
-	    set +e
-	    # Retry up to 10 times because Curl has a tendency to timeout on
-	    # Github runners.
-	    for retry in {1..10} error; do
-	        if [[ $retry == "error" ]]; then exit 5; fi
-	        curl --http1.1 -LSs \
-		    "https://dl.google.com/android/repository/android-ndk-r16b-${platform}-x86_64.zip" \
-		    --output /tmp/android-ndk-r16b.zip && break
-	        sleep 300
-	    done
-	    set -e
-	    (cd /tmp && unzip -oq android-ndk-r16b.zip && rm -f android-ndk-r16b.zip)
-	    echo "NDK r16b has been downloaded into /tmp/android-ndk-r16b"
+        echo "This build recommends NDK r21e, downloading..."
+            if [[ -z $(which curl) ]]; then
+                echo "Error, could not run 'curl' to download NDK. Is it in your PATH?"
+                exit 1
+            fi
+            set +e
+            # Retry up to 10 times because Curl has a tendency to timeout on
+            # Github runners.
+            for retry in {1..10} error; do
+                if [[ $retry == "error" ]]; then exit 5; fi
+                curl --http1.1 -LSs \
+                    "https://dl.google.com/android/repository/android-ndk-r21e-${platform}-x86_64.zip" \
+                    --output /tmp/android-ndk-r21e.zip && break
+                sleep 300
+            done
+            set -e
+            (cd /tmp && unzip -oq android-ndk-r21e.zip && rm -f android-ndk-r21e.zip)
+            echo "NDK r21e has been downloaded into /tmp/android-ndk-r21e"
     fi
 fi
diff --git a/build_scripts/android/package.sh b/build_scripts/android/package.sh
index 220e6181ed..553b9aca56 100755
--- a/build_scripts/android/package.sh
+++ b/build_scripts/android/package.sh
@@ -2,22 +2,14 @@
 
 # Copyright 2020 Google LLC
 
-readonly -a allowed_stl_variants=("c++" "gnustl")
 builtpath=$1
 packagepath=$2
-stl=$3
 
-if [[ -z "${builtpath}" || -z "${packagepath}" || -z "${stl}" ]]; then
-    echo "Usage: $0 <built Android SDK path> <path to put packaged files into> <STL variant>"
-    echo "STL variant is one of: ${allowed_stl_variants[*]}"
+if [[ -z "${builtpath}" || -z "${packagepath}" ]]; then
+    echo "Usage: $0 <built Android SDK path> <path to put packaged files into>"
     exit 1
 fi
 
-if [[ ! " ${allowed_stl_variants[@]} " =~ " ${stl} " ]]; then
-    echo "Invalid STL variant '${stl}'. Allowed STL variants: ${allowed_stl_variants[*]}"
-    exit 2
-fi
-
 if [[ ! -d "${builtpath}/app/build" ]]; then
     echo "Built Android SDK not found at path '${builtpath}'."
     exit 2
@@ -38,7 +30,7 @@ cd "${origpath}"
 
 mkdir -p "${destpath}/libs/android"
 
-# Copy each platform's libraries to the destination directory for this STL variant.
+# Copy each platform's libraries to the destination directory.
 cd "${sourcepath}"
 # Make sure we only copy the libraries in product_list (specified in packaging.conf)
 for product in ${product_list[*]}; do
@@ -49,7 +41,7 @@ for product in ${product_list[*]}; do
     for cpudir in "${dir}"/*; do
 	cpu=$(basename ${cpudir})
 	libsrc="${sourcepath}/${cpudir}/libfirebase_${product}.a"
-	libdest="${destpath}/libs/android/${cpu}/${stl}"
+	libdest="${destpath}/libs/android/${cpu}"
 	mkdir -p "${libdest}"
 	cp -f "${libsrc}" "${libdest}/"
     done
diff --git a/build_scripts/desktop/get_variant.sh b/build_scripts/desktop/get_variant.sh
index 981dbffaf3..16db1f6a75 100755
--- a/build_scripts/desktop/get_variant.sh
+++ b/build_scripts/desktop/get_variant.sh
@@ -124,9 +124,6 @@ for c in $(echo "${filename}" | tr "[:upper:]" "[:lower:]" | tr "_.-" "\n\n\n");
 	c++)
 	    stl=c++
         ;;
-	gnustl)
-	    stl=gnustl
-        ;;
 	cxx11)
 	    linux_abi=cxx11
         ;;
@@ -187,9 +184,9 @@ case ${os} in
     ;;
     android)
 	if [[ -z "${arch}" ]]; then
-	    echo -n "${stl}"
+	    echo -n "."
 	else
-	    echo -n "${arch}/${stl}"
+	    echo -n "${arch}"
 	fi
     ;;
     *)
diff --git a/database/build.gradle b/database/build.gradle
index 8739434d0f..bafe7785db 100644
--- a/database/build.gradle
+++ b/database/build.gradle
@@ -30,11 +30,6 @@ allprojects {
 
 apply plugin: 'com.android.library'
 
-ext {
-  firebaseAndroidStl = System.getenv('FIREBASE_ANDROID_STL')
-  firebaseAndroidStl = firebaseAndroidStl != null ? firebaseAndroidStl : ''
-}
-
 android {
   compileSdkVersion 28
   buildToolsVersion '28.0.3'
@@ -71,8 +66,7 @@ android {
         //           Only include needed project.
         arguments '-DFIREBASE_CPP_USE_PRIOR_GRADLE_BUILD=ON',
                 '-DFIREBASE_INCLUDE_LIBRARY_DEFAULT=OFF',
-                '-DFIREBASE_INCLUDE_DATABASE=ON',
-		"-DFIREBASE_ANDROID_STL=${firebaseAndroidStl}"
+                '-DFIREBASE_INCLUDE_DATABASE=ON'
       }
     }
   }
diff --git a/dynamic_links/build.gradle b/dynamic_links/build.gradle
index 1db97b2d96..570514f91d 100644
--- a/dynamic_links/build.gradle
+++ b/dynamic_links/build.gradle
@@ -30,11 +30,6 @@ allprojects {
 
 apply plugin: 'com.android.library'
 
-ext {
-  firebaseAndroidStl = System.getenv('FIREBASE_ANDROID_STL')
-  firebaseAndroidStl = firebaseAndroidStl != null ? firebaseAndroidStl : ''
-}
-
 android {
   compileSdkVersion 28
   buildToolsVersion '28.0.3'
@@ -71,8 +66,7 @@ android {
         //           Only include needed project.
         arguments '-DFIREBASE_CPP_USE_PRIOR_GRADLE_BUILD=ON',
                 '-DFIREBASE_INCLUDE_LIBRARY_DEFAULT=OFF',
-                '-DFIREBASE_INCLUDE_DYNAMIC_LINKS=ON',
-		"-DFIREBASE_ANDROID_STL=${firebaseAndroidStl}"
+                '-DFIREBASE_INCLUDE_DYNAMIC_LINKS=ON'
       }
     }
   }
diff --git a/firestore/build.gradle b/firestore/build.gradle
index 13b22de7c8..a06792599a 100644
--- a/firestore/build.gradle
+++ b/firestore/build.gradle
@@ -30,11 +30,6 @@ allprojects {
 
 apply plugin: 'com.android.library'
 
-ext {
-  firebaseAndroidStl = System.getenv('FIREBASE_ANDROID_STL')
-  firebaseAndroidStl = firebaseAndroidStl != null ? firebaseAndroidStl : ''
-}
-
 android {
   compileSdkVersion 28
   buildToolsVersion '28.0.3'
@@ -72,8 +67,7 @@ android {
         //           Only include needed project.
         arguments '-DFIREBASE_CPP_USE_PRIOR_GRADLE_BUILD=ON',
                 '-DFIREBASE_INCLUDE_LIBRARY_DEFAULT=OFF',
-                '-DFIREBASE_INCLUDE_FIRESTORE=ON',
-		"-DFIREBASE_ANDROID_STL=${firebaseAndroidStl}"
+                '-DFIREBASE_INCLUDE_FIRESTORE=ON'
       }
     }
   }
diff --git a/functions/build.gradle b/functions/build.gradle
index c350b092f1..0376db0837 100644
--- a/functions/build.gradle
+++ b/functions/build.gradle
@@ -30,11 +30,6 @@ allprojects {
 
 apply plugin: 'com.android.library'
 
-ext {
-  firebaseAndroidStl = System.getenv('FIREBASE_ANDROID_STL')
-  firebaseAndroidStl = firebaseAndroidStl != null ? firebaseAndroidStl : ''
-}
-
 android {
   compileSdkVersion 28
   buildToolsVersion '28.0.3'
@@ -71,8 +66,7 @@ android {
         //           Only include needed project.
         arguments '-DFIREBASE_CPP_USE_PRIOR_GRADLE_BUILD=ON',
                 '-DFIREBASE_INCLUDE_LIBRARY_DEFAULT=OFF',
-                '-DFIREBASE_INCLUDE_FUNCTIONS=ON',
-		"-DFIREBASE_ANDROID_STL=${firebaseAndroidStl}"
+                '-DFIREBASE_INCLUDE_FUNCTIONS=ON'
       }
     }
   }
diff --git a/installations/build.gradle b/installations/build.gradle
index 783689c6d4..123c87465a 100644
--- a/installations/build.gradle
+++ b/installations/build.gradle
@@ -30,11 +30,6 @@ allprojects {
 
 apply plugin: 'com.android.library'
 
-ext {
-  firebaseAndroidStl = System.getenv('FIREBASE_ANDROID_STL')
-  firebaseAndroidStl = firebaseAndroidStl != null ? firebaseAndroidStl : ''
-}
-
 android {
   compileSdkVersion 28
   buildToolsVersion '28.0.3'
@@ -71,8 +66,7 @@ android {
         //           Only include needed project.
         arguments '-DFIREBASE_CPP_USE_PRIOR_GRADLE_BUILD=ON',
                 '-DFIREBASE_INCLUDE_LIBRARY_DEFAULT=OFF',
-                '-DFIREBASE_INCLUDE_INSTALLATIONS=ON',
-                "-DFIREBASE_ANDROID_STL=${firebaseAndroidStl}"
+                '-DFIREBASE_INCLUDE_INSTALLATIONS=ON'
       }
     }
   }
diff --git a/messaging/build.gradle b/messaging/build.gradle
index e6399fc77a..238265ca37 100644
--- a/messaging/build.gradle
+++ b/messaging/build.gradle
@@ -30,11 +30,6 @@ allprojects {
 
 apply plugin: 'com.android.library'
 
-ext {
-  firebaseAndroidStl = System.getenv('FIREBASE_ANDROID_STL')
-  firebaseAndroidStl = firebaseAndroidStl != null ? firebaseAndroidStl : ''
-}
-
 android {
   compileSdkVersion 28
   buildToolsVersion '28.0.3'
@@ -71,8 +66,7 @@ android {
         //           Only include needed project.
         arguments '-DFIREBASE_CPP_USE_PRIOR_GRADLE_BUILD=ON',
                 '-DFIREBASE_INCLUDE_LIBRARY_DEFAULT=OFF',
-                '-DFIREBASE_INCLUDE_MESSAGING=ON',
-		"-DFIREBASE_ANDROID_STL=${firebaseAndroidStl}"
+                '-DFIREBASE_INCLUDE_MESSAGING=ON'
       }
     }
   }
diff --git a/release_build_files/CMakeLists.txt b/release_build_files/CMakeLists.txt
index 239acca6ea..fae75b12e8 100644
--- a/release_build_files/CMakeLists.txt
+++ b/release_build_files/CMakeLists.txt
@@ -24,10 +24,8 @@ endif ()
 
 # Determine the location of the libraries to use based on the platform.
 if(ANDROID)
-  string(REPLACE "_" ";" SPLIT_STL ${ANDROID_STL})
-  list(GET SPLIT_STL 0 STL_DIR)
   set(FIREBASE_SDK_LIBDIR
-      "${FIREBASE_CPP_SDK_DIR}/libs/android/${ANDROID_ABI}/${STL_DIR}")
+      "${FIREBASE_CPP_SDK_DIR}/libs/android/${ANDROID_ABI}")
 elseif(APPLE)
   if(IOS)
     set(FIREBASE_SDK_LIBDIR ${FIREBASE_CPP_SDK_DIR}/libs/ios/universal)
diff --git a/release_build_files/readme.md b/release_build_files/readme.md
index f167b6c9e7..df49e73326 100644
--- a/release_build_files/readme.md
+++ b/release_build_files/readme.md
@@ -50,12 +50,9 @@ libs/ios/ARCH             | iOS static libraries (compiled against
 |                         | libc++)
 |                         | Multi-architecture libraries are
 |                         | provided in the *universal* directory.
-libs/android/ARCH/STL     | Android (GCC 4.8+ compatible) static
-|                         | libraries for each architecture and STL
-|                         | variant.
-|                         | _STL variants available:_
-|                         | * `c++`: LLVM libc++ runtime (recommended)
-|                         | * `gnustl`: GNU STL (deprecated)
+libs/android/ARCH         | Android (GCC 4.8+ compatible) static
+|                         | libraries for each architecture. Only the
+|                         | LLVM libc++ STL runtime ("c++") is supported.
 |                         | More information can be found in the
 |                         | [NDK C++ Helper Runtimes](https://developer.android.com/ndk/guides/cpp-support.html#runtimes)
 |                         | documentation.
@@ -567,8 +564,13 @@ workflow use only during the development of your app, not for publicly shipping
 code.
 
 ## Release Notes
-### Upcoming release
+### 9.0.0
 -   Changes
+    -   General (Android): On Android, Firebase C++ is now built against NDK
+        version r21e.
+    -   General (Android): Firebase support for gnustl (also known as libstdc++)
+        has been removed. Please use libc++ instead. Android libraries have been
+	moved from libs/android/ARCH/STL to libs/android/ARCH.
     -   Storage (Desktop): Set Content-Type HTTP header when uploading with
         custom metadata.
 
diff --git a/remote_config/build.gradle b/remote_config/build.gradle
index 28f582eff4..35c1790010 100644
--- a/remote_config/build.gradle
+++ b/remote_config/build.gradle
@@ -30,11 +30,6 @@ allprojects {
 
 apply plugin: 'com.android.library'
 
-ext {
-  firebaseAndroidStl = System.getenv('FIREBASE_ANDROID_STL')
-  firebaseAndroidStl = firebaseAndroidStl != null ? firebaseAndroidStl : ''
-}
-
 android {
   compileSdkVersion 28
   buildToolsVersion '28.0.3'
@@ -71,8 +66,7 @@ android {
         //           Only include needed project.
         arguments '-DFIREBASE_CPP_USE_PRIOR_GRADLE_BUILD=ON',
                 '-DFIREBASE_INCLUDE_LIBRARY_DEFAULT=OFF',
-                '-DFIREBASE_INCLUDE_REMOTE_CONFIG=ON',
-		"-DFIREBASE_ANDROID_STL=${firebaseAndroidStl}"
+                '-DFIREBASE_INCLUDE_REMOTE_CONFIG=ON'
       }
     }
   }
diff --git a/storage/build.gradle b/storage/build.gradle
index 2c2b6bc50a..0e3b9a0da7 100644
--- a/storage/build.gradle
+++ b/storage/build.gradle
@@ -30,11 +30,6 @@ allprojects {
 
 apply plugin: 'com.android.library'
 
-ext {
-  firebaseAndroidStl = System.getenv('FIREBASE_ANDROID_STL')
-  firebaseAndroidStl = firebaseAndroidStl != null ? firebaseAndroidStl : ''
-}
-
 android {
   compileSdkVersion 28
   buildToolsVersion '28.0.3'
@@ -71,8 +66,7 @@ android {
         //           Only include needed project.
         arguments '-DFIREBASE_CPP_USE_PRIOR_GRADLE_BUILD=ON',
                 '-DFIREBASE_INCLUDE_LIBRARY_DEFAULT=OFF',
-                '-DFIREBASE_INCLUDE_STORAGE=ON',
-		"-DFIREBASE_ANDROID_STL=${firebaseAndroidStl}"
+                '-DFIREBASE_INCLUDE_STORAGE=ON'
       }
     }
   }