diff --git a/modules/integrations/arrow-integrations-retrofit-adapter/build.gradle b/modules/integrations/arrow-integrations-retrofit-adapter/build.gradle
new file mode 100644
index 00000000000..84d3a4f25aa
--- /dev/null
+++ b/modules/integrations/arrow-integrations-retrofit-adapter/build.gradle
@@ -0,0 +1,22 @@
+def retrofitVersion = "2.4.0"
+
+dependencies {
+    compile project(':arrow-effects')
+    compile project(':arrow-typeclasses')
+    compile "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlinVersion"
+    compile project(':arrow-annotations')
+    compile "com.squareup.retrofit2:retrofit:$retrofitVersion"
+    kapt project(':arrow-annotations-processor')
+    kaptTest project(':arrow-annotations-processor')
+    compileOnly project(':arrow-annotations-processor')
+    testCompileOnly project(':arrow-annotations-processor')
+    testCompile project(':arrow-test')
+    testCompile "com.squareup.retrofit2:converter-gson:$retrofitVersion"
+    testCompile 'com.squareup.okhttp3:mockwebserver:3.11.0'
+    testCompile project(':arrow-effects-rx2')
+    testCompile project(':arrow-effects-rx2-instances')
+    testCompile project(':arrow-effects-instances')
+}
+
+apply from: rootProject.file('gradle/gradle-mvn-push.gradle')
+apply plugin: 'kotlin-kapt'
\ No newline at end of file
diff --git a/modules/integrations/arrow-integrations-retrofit-adapter/gradle.properties b/modules/integrations/arrow-integrations-retrofit-adapter/gradle.properties
new file mode 100644
index 00000000000..10160a6a5c7
--- /dev/null
+++ b/modules/integrations/arrow-integrations-retrofit-adapter/gradle.properties
@@ -0,0 +1,4 @@
+# Maven publishing configuration
+POM_NAME=Arrow-Integrations-Retrofit-Adapter
+POM_ARTIFACT_ID=arrow-integration-retrofit-adapter
+POM_PACKAGING=jar
diff --git a/modules/integrations/arrow-integrations-retrofit-adapter/src/main/kotlin/arrow/integrations/retrofit/adapter/CallK.kt b/modules/integrations/arrow-integrations-retrofit-adapter/src/main/kotlin/arrow/integrations/retrofit/adapter/CallK.kt
new file mode 100644
index 00000000000..2a62f29bf20
--- /dev/null
+++ b/modules/integrations/arrow-integrations-retrofit-adapter/src/main/kotlin/arrow/integrations/retrofit/adapter/CallK.kt
@@ -0,0 +1,16 @@
+package arrow.integrations.retrofit.adapter
+
+import arrow.Kind
+import arrow.effects.typeclasses.Async
+import arrow.effects.typeclasses.MonadDefer
+import arrow.typeclasses.MonadError
+import retrofit2.Call
+import retrofit2.Response
+
+data class CallK<R>(val call: Call<R>) {
+  fun <F> async(AC: Async<F>): Kind<F, Response<R>> = call.runAsync(AC)
+
+  fun <F> defer(defer: MonadDefer<F>): Kind<F, Response<R>> = call.runSyncDeferred(defer)
+
+  fun <F> catch(monadError: MonadError<F, Throwable>): Kind<F, Response<R>> = call.runSyncCatch(monadError)
+}
diff --git a/modules/integrations/arrow-integrations-retrofit-adapter/src/main/kotlin/arrow/integrations/retrofit/adapter/CallKind2CallAdapter.kt b/modules/integrations/arrow-integrations-retrofit-adapter/src/main/kotlin/arrow/integrations/retrofit/adapter/CallKind2CallAdapter.kt
new file mode 100644
index 00000000000..a13166718cf
--- /dev/null
+++ b/modules/integrations/arrow-integrations-retrofit-adapter/src/main/kotlin/arrow/integrations/retrofit/adapter/CallKind2CallAdapter.kt
@@ -0,0 +1,11 @@
+package arrow.integrations.retrofit.adapter
+
+import retrofit2.Call
+import retrofit2.CallAdapter
+import java.lang.reflect.Type
+
+class CallKind2CallAdapter<R>(private val type: Type) : CallAdapter<R, CallK<R>> {
+  override fun adapt(call: Call<R>): CallK<R> = CallK(call)
+
+  override fun responseType(): Type = type
+}
diff --git a/modules/integrations/arrow-integrations-retrofit-adapter/src/main/kotlin/arrow/integrations/retrofit/adapter/CallKindAdapterFactory.kt b/modules/integrations/arrow-integrations-retrofit-adapter/src/main/kotlin/arrow/integrations/retrofit/adapter/CallKindAdapterFactory.kt
new file mode 100644
index 00000000000..42a32187f86
--- /dev/null
+++ b/modules/integrations/arrow-integrations-retrofit-adapter/src/main/kotlin/arrow/integrations/retrofit/adapter/CallKindAdapterFactory.kt
@@ -0,0 +1,36 @@
+package arrow.integrations.retrofit.adapter
+
+import retrofit2.CallAdapter
+import retrofit2.Retrofit
+import java.lang.reflect.ParameterizedType
+import java.lang.reflect.Type
+
+class Async2CallAdapterFactory : CallAdapter.Factory() {
+
+  companion object {
+    fun create(): Async2CallAdapterFactory = Async2CallAdapterFactory()
+  }
+
+  override fun get(returnType: Type, annotations: Array<Annotation>, retrofit: Retrofit): CallAdapter<*, *>? {
+    val rawType = CallAdapter.Factory.getRawType(returnType)
+
+    if (returnType !is ParameterizedType) {
+      val name = parseTypeName(returnType)
+      throw IllegalArgumentException("Return type must be parameterized as " +
+        "$name<Foo> or $name<out Foo>")
+    }
+
+    val effectType = CallAdapter.Factory.getParameterUpperBound(0, returnType)
+
+    return if (rawType == CallK::class.java) {
+      CallKind2CallAdapter<Type>(effectType)
+    } else {
+      null
+    }
+  }
+}
+
+private fun parseTypeName(type: Type) =
+  type.typeName
+    .split(".")
+    .last()
diff --git a/modules/integrations/arrow-integrations-retrofit-adapter/src/main/kotlin/arrow/integrations/retrofit/adapter/ResponseCallback.kt b/modules/integrations/arrow-integrations-retrofit-adapter/src/main/kotlin/arrow/integrations/retrofit/adapter/ResponseCallback.kt
new file mode 100644
index 00000000000..c4a4ccf4672
--- /dev/null
+++ b/modules/integrations/arrow-integrations-retrofit-adapter/src/main/kotlin/arrow/integrations/retrofit/adapter/ResponseCallback.kt
@@ -0,0 +1,18 @@
+package arrow.integrations.retrofit.adapter
+
+import arrow.core.Either
+import arrow.core.left
+import arrow.core.right
+import retrofit2.Call
+import retrofit2.Callback
+import retrofit2.Response
+
+class ResponseCallback<R>(private val proc: (Either<Throwable, Response<R>>) -> Unit) : Callback<R> {
+  override fun onResponse(call: Call<R>, response: Response<R>) {
+    proc(response.right())
+  }
+
+  override fun onFailure(call: Call<R>, throwable: Throwable) {
+    proc(throwable.left())
+  }
+}
diff --git a/modules/integrations/arrow-integrations-retrofit-adapter/src/main/kotlin/arrow/integrations/retrofit/adapter/syntax.kt b/modules/integrations/arrow-integrations-retrofit-adapter/src/main/kotlin/arrow/integrations/retrofit/adapter/syntax.kt
new file mode 100644
index 00000000000..9d9e94aa57b
--- /dev/null
+++ b/modules/integrations/arrow-integrations-retrofit-adapter/src/main/kotlin/arrow/integrations/retrofit/adapter/syntax.kt
@@ -0,0 +1,36 @@
+package arrow.integrations.retrofit.adapter
+
+import arrow.Kind
+import arrow.effects.typeclasses.Async
+import arrow.effects.typeclasses.MonadDefer
+import arrow.typeclasses.ApplicativeError
+import arrow.typeclasses.MonadError
+import retrofit2.Call
+import retrofit2.HttpException
+import retrofit2.Response
+
+fun <F, R> Response<R>.unwrapBody(apError: ApplicativeError<F, Throwable>): Kind<F, R> =
+  if (this.isSuccessful) {
+    val body = this.body()
+    if (body != null) {
+      apError.just(body)
+    } else {
+      apError.raiseError(IllegalStateException("The request returned a null body"))
+    }
+  } else {
+    apError.raiseError(HttpException(this))
+  }
+
+fun <F, A> Call<A>.runAsync(AC: Async<F>): Kind<F, Response<A>> =
+  AC.async { callback ->
+    enqueue(ResponseCallback(callback))
+  }
+
+fun <F, A> Call<A>.runSyncDeferred(defer: MonadDefer<F>): Kind<F, Response<A>> = defer { execute() }
+
+fun <F, A> Call<A>.runSyncCatch(monadError: MonadError<F, Throwable>): Kind<F, Response<A>> =
+  monadError.run {
+    catch {
+      execute()
+    }
+  }
diff --git a/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/Async2CallAdapterFactoryTest.kt b/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/Async2CallAdapterFactoryTest.kt
new file mode 100644
index 00000000000..3fb80bd5fc1
--- /dev/null
+++ b/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/Async2CallAdapterFactoryTest.kt
@@ -0,0 +1,42 @@
+package arrow.integrations.retrofit.adapter
+
+import arrow.effects.IO
+import arrow.integrations.retrofit.adapter.retrofit.retrofit
+import arrow.test.UnitSpec
+import com.google.common.reflect.TypeToken
+import io.kotlintest.KTestJUnitRunner
+import io.kotlintest.matchers.shouldBe
+import io.kotlintest.matchers.shouldThrow
+import okhttp3.HttpUrl
+import org.junit.runner.RunWith
+
+private val NO_ANNOTATIONS = emptyArray<Annotation>()
+
+private val retrofit = retrofit(HttpUrl.parse("http://localhost:1")!!)
+private val factory = Async2CallAdapterFactory.create()
+
+@RunWith(KTestJUnitRunner::class)
+class Async2CallAdapterFactoryTest : UnitSpec() {
+  init {
+    "Non CallK Class should return null" {
+      factory.get(object : TypeToken<List<String>>() {}.type, NO_ANNOTATIONS, retrofit) shouldBe null
+    }
+
+    "Non parametrized type should throw exception" {
+      val exceptionList = shouldThrow<IllegalArgumentException> {
+        factory.get(List::class.java, NO_ANNOTATIONS, retrofit)
+      }
+      exceptionList.message shouldBe "Return type must be parameterized as List<Foo> or List<out Foo>"
+
+      val exceptionIO = shouldThrow<IllegalArgumentException> {
+        factory.get(IO::class.java, NO_ANNOTATIONS, retrofit)
+      }
+      exceptionIO.message shouldBe "Return type must be parameterized as IO<Foo> or IO<out Foo>"
+    }
+
+    "Should work for CallK types" {
+      factory.get(object : TypeToken<CallK<String>>() {}.type, NO_ANNOTATIONS, retrofit)!!
+        .responseType() shouldBe String::class.java
+    }
+  }
+}
diff --git a/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/ProcCallBackTest.kt b/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/ProcCallBackTest.kt
new file mode 100644
index 00000000000..9f1faa058f9
--- /dev/null
+++ b/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/ProcCallBackTest.kt
@@ -0,0 +1,74 @@
+package arrow.integrations.retrofit.adapter
+
+import arrow.core.Either
+import arrow.core.fix
+import arrow.effects.IO
+import arrow.effects.ObservableK
+import arrow.effects.fix
+import arrow.effects.instances.io.async.async
+import arrow.effects.observablek.applicativeError.applicativeError
+import arrow.effects.observablek.monadDefer.monadDefer
+import arrow.instances.either.applicativeError.applicativeError
+import arrow.integrations.retrofit.adapter.mock.ResponseMock
+import arrow.integrations.retrofit.adapter.retrofit.ApiClientTest
+import arrow.integrations.retrofit.adapter.retrofit.retrofit
+import arrow.test.UnitSpec
+import io.kotlintest.KTestJUnitRunner
+import io.kotlintest.matchers.fail
+import okhttp3.HttpUrl
+import okhttp3.mockwebserver.MockResponse
+import okhttp3.mockwebserver.MockWebServer
+import org.junit.Assert.assertEquals
+import org.junit.runner.RunWith
+
+@RunWith(KTestJUnitRunner::class)
+class ProcCallBackTest : UnitSpec() {
+  private val server = MockWebServer().apply {
+    enqueue(MockResponse().setBody("{\"response\":  \"hello, world!\"}").setResponseCode(200))
+    start()
+  }
+
+  private val baseUrl: HttpUrl = server.url("/")
+
+  init {
+    "should be able to parse answer with ForIO" {
+      createApiClientTest(baseUrl)
+        .testCallK()
+        .async(IO.async())
+        .fix()
+        .unsafeRunSync()
+        .unwrapBody(Either.applicativeError())
+        .fix()
+        .fold({ throwable ->
+          fail("The requested terminated with an exception. Message: ${throwable.message}")
+        }, { responseMock ->
+          assertEquals(ResponseMock("hello, world!"), responseMock)
+        })
+    }
+
+    "should be able to parse answer with ForObservableK" {
+      with(ObservableK) {
+        createApiClientTest(baseUrl)
+          .testCallK()
+          .defer(monadDefer())
+          .fix()
+          .flatMap { response ->
+            response.unwrapBody(applicativeError()).fix()
+          }
+          .observable
+          .test()
+          .assertValue(ResponseMock("hello, world!"))
+      }
+    }
+
+    "should be able to run a POST with UNIT as response" {
+      createApiClientTest(baseUrl)
+        .testIOResponsePost()
+        .async(IO.async())
+        .fix()
+        .unsafeRunSync()
+    }
+  }
+}
+
+private fun createApiClientTest(baseUrl: HttpUrl) = retrofit(baseUrl).create(ApiClientTest::class.java)
diff --git a/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/ResponseCallbackTest.kt b/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/ResponseCallbackTest.kt
new file mode 100644
index 00000000000..24c4a4b8e89
--- /dev/null
+++ b/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/ResponseCallbackTest.kt
@@ -0,0 +1,41 @@
+package arrow.integrations.retrofit.adapter
+
+import arrow.effects.IO
+import arrow.effects.fix
+import arrow.effects.instances.io.async.async
+import arrow.integrations.retrofit.adapter.retrofit.ApiClientTest
+import arrow.integrations.retrofit.adapter.retrofit.retrofit
+import arrow.test.UnitSpec
+import io.kotlintest.KTestJUnitRunner
+import io.kotlintest.matchers.fail
+import okhttp3.HttpUrl
+import okhttp3.mockwebserver.MockResponse
+import okhttp3.mockwebserver.MockWebServer
+import org.junit.runner.RunWith
+
+@RunWith(KTestJUnitRunner::class)
+class ResponseCallbackTest : UnitSpec() {
+  private val server = MockWebServer().apply {
+    enqueue(MockResponse().setBody("{response:  \"hello, world!\"}").setResponseCode(200))
+    start()
+  }
+
+  private val baseUrl: HttpUrl = server.url("/")
+
+  init {
+    "bad deserialization should return Either.Left" {
+      createApiClientTest(baseUrl)
+        .testCallK()
+        .async(IO.async())
+        .fix()
+        .attempt()
+        .unsafeRunSync()
+        .fold({
+        }, {
+          fail("The request should have not terminated correctly")
+        })
+    }
+  }
+}
+
+private fun createApiClientTest(baseUrl: HttpUrl) = retrofit(baseUrl).create(ApiClientTest::class.java)
diff --git a/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/mock/ResponseMock.kt b/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/mock/ResponseMock.kt
new file mode 100644
index 00000000000..9bef63d208b
--- /dev/null
+++ b/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/mock/ResponseMock.kt
@@ -0,0 +1,3 @@
+package arrow.integrations.retrofit.adapter.mock
+
+data class ResponseMock(val response: String)
diff --git a/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/retrofit/ApiClientTest.kt b/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/retrofit/ApiClientTest.kt
new file mode 100644
index 00000000000..2897e792f11
--- /dev/null
+++ b/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/retrofit/ApiClientTest.kt
@@ -0,0 +1,19 @@
+package arrow.integrations.retrofit.adapter.retrofit
+
+import arrow.integrations.retrofit.adapter.CallK
+import arrow.integrations.retrofit.adapter.mock.ResponseMock
+import retrofit2.http.GET
+import retrofit2.http.POST
+
+interface ApiClientTest {
+
+  @GET("test")
+  fun testCallK(): CallK<ResponseMock>
+
+  @GET("testCallKResponse")
+  fun testCallKResponse(): CallK<ResponseMock>
+
+  @POST("testIOResponsePOST")
+  fun testIOResponsePost(): CallK<Unit>
+
+}
diff --git a/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/retrofit/Retrofit.kt b/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/retrofit/Retrofit.kt
new file mode 100644
index 00000000000..e079cfc80a6
--- /dev/null
+++ b/modules/integrations/arrow-integrations-retrofit-adapter/src/test/kotlin/arrow/integrations/retrofit/adapter/retrofit/Retrofit.kt
@@ -0,0 +1,20 @@
+package arrow.integrations.retrofit.adapter.retrofit
+
+import arrow.integrations.retrofit.adapter.Async2CallAdapterFactory
+import okhttp3.HttpUrl
+import okhttp3.OkHttpClient
+import retrofit2.Retrofit
+import retrofit2.converter.gson.GsonConverterFactory
+
+private fun provideOkHttpClient(): OkHttpClient =
+  OkHttpClient.Builder().build()
+
+private fun configRetrofit(retrofitBuilder: Retrofit.Builder) =
+  retrofitBuilder
+    .addCallAdapterFactory(Async2CallAdapterFactory.create())
+    .addConverterFactory(GsonConverterFactory.create())
+    .client(provideOkHttpClient())
+
+private fun getRetrofitBuilderDefaults(baseUrl: HttpUrl) = Retrofit.Builder().baseUrl(baseUrl)
+
+fun retrofit(baseUrl: HttpUrl): Retrofit = configRetrofit(getRetrofitBuilderDefaults(baseUrl)).build()
diff --git a/settings.gradle b/settings.gradle
index 234a9fd6a83..44609c66d7a 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -65,6 +65,10 @@ include {
             _ 'effects-reactor-instances'
         }
 
+        integrations {
+            _ 'integrations-retrofit-adapter'
+        }
+
         folder('recursion-schemes') {
             _ 'recursion'
             _ 'instances-recursion'