diff --git a/.gitignore b/.gitignore
index 8e206315de..a3d8e995e6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -20,8 +20,9 @@ _notes/
 __pycache__/
 *.pyc
 
-# except for .gitignore
+# except for .gitignore and .readthedocs.yml
 !/.gitignore
+!.readthedocs.yml
 
 # except for .tx/config
 !/.tx/
diff --git a/.readthedocs.yml b/.readthedocs.yml
new file mode 100644
index 0000000000..ee2ddc2248
--- /dev/null
+++ b/.readthedocs.yml
@@ -0,0 +1,16 @@
+# Configuration for the Read The Docs (RTD) builds of the documentation.
+# Ref: https://docs.readthedocs.io/en/stable/config-file/v2.html
+# The python.install.requirements pins the version of Sphinx used.
+version: 2
+
+build:
+  os: ubuntu-20.04
+  tools:
+    python: "3.9"
+
+sphinx:
+  configuration: docs/source/conf.py
+
+python:
+  install:
+    - requirements: docs/requirements.txt
diff --git a/docs/requirements.txt b/docs/requirements.txt
new file mode 100644
index 0000000000..5092ac8f12
--- /dev/null
+++ b/docs/requirements.txt
@@ -0,0 +1 @@
+Sphinx>=4.3.1