diff --git a/.idea/gradle.xml b/.idea/gradle.xml
index 69ac663..68a7b59 100644
--- a/.idea/gradle.xml
+++ b/.idea/gradle.xml
@@ -30,6 +30,7 @@
             <option value="$PROJECT_DIR$/dachlatten-flow" />
             <option value="$PROJECT_DIR$/dachlatten-google" />
             <option value="$PROJECT_DIR$/dachlatten-primitives" />
+            <option value="$PROJECT_DIR$/dachlatten-retrofit" />
           </set>
         </option>
         <option name="resolveExternalAnnotations" value="false" />
diff --git a/dachlatten-retrofit/build.gradle.kts b/dachlatten-retrofit/build.gradle.kts
new file mode 100644
index 0000000..ba3a813
--- /dev/null
+++ b/dachlatten-retrofit/build.gradle.kts
@@ -0,0 +1,15 @@
+plugins {
+    id("android-library-base")
+    id("android-library-unit-test")
+    id("android-library-release")
+    alias(libs.plugins.kotlin.serialization.plugin)
+}
+
+dependencies {
+    implementation(libs.kotlinx.serialization)
+    implementation(libs.retrofit.serialization)
+    implementation(libs.okhttp)
+
+    testImplementation(libs.kotlinx.serialization)
+    testImplementation(libs.okhttp.mockwebserver)
+}
diff --git a/dachlatten-retrofit/src/main/kotlin/de/sipgate/dachlatten/okhttp/StreamingJsonConverterFactory.kt b/dachlatten-retrofit/src/main/kotlin/de/sipgate/dachlatten/okhttp/StreamingJsonConverterFactory.kt
new file mode 100644
index 0000000..e4dc1b5
--- /dev/null
+++ b/dachlatten-retrofit/src/main/kotlin/de/sipgate/dachlatten/okhttp/StreamingJsonConverterFactory.kt
@@ -0,0 +1,50 @@
+package de.sipgate.dachlatten.okhttp
+
+import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.decodeFromStream
+import kotlinx.serialization.json.encodeToStream
+import kotlinx.serialization.serializer
+import okhttp3.MediaType
+import okhttp3.RequestBody
+import okhttp3.RequestBody.Companion.toRequestBody
+import okhttp3.ResponseBody
+import retrofit2.Converter
+import retrofit2.Retrofit
+import java.io.ByteArrayOutputStream
+import java.lang.reflect.Type
+
+@JvmName("convert")
+@ExperimentalSerializationApi
+fun Json.asConverterFactory(contentType: MediaType): Converter.Factory =
+    object : Converter.Factory() {
+        override fun responseBodyConverter(
+            type: Type,
+            annotations: Array<out Annotation>,
+            retrofit: Retrofit,
+        ) = Converter<ResponseBody, Any> { value ->
+            this@asConverterFactory.decodeFromStream(
+                this@asConverterFactory.serializersModule.serializer(type),
+                value.byteStream(),
+            )
+        }
+
+        override fun requestBodyConverter(
+            type: Type,
+            parameterAnnotations: Array<out Annotation>,
+            methodAnnotations: Array<out Annotation>,
+            retrofit: Retrofit,
+        ) = Converter<Any, RequestBody> { value ->
+            val stream = ByteArrayOutputStream()
+            this@asConverterFactory.encodeToStream(
+                this@asConverterFactory.serializersModule.serializer(type),
+                value,
+                stream,
+            )
+            stream.toByteArray().toRequestBody(
+                contentType,
+                0,
+                stream.size(),
+            )
+        }
+    }
diff --git a/dachlatten-retrofit/src/test/kotlin/de/sipgate/dachlatten/okhttp/KotlinSerializationConverterFactoryStringTest.kt b/dachlatten-retrofit/src/test/kotlin/de/sipgate/dachlatten/okhttp/KotlinSerializationConverterFactoryStringTest.kt
new file mode 100644
index 0000000..d5b0a74
--- /dev/null
+++ b/dachlatten-retrofit/src/test/kotlin/de/sipgate/dachlatten/okhttp/KotlinSerializationConverterFactoryStringTest.kt
@@ -0,0 +1,60 @@
+package de.sipgate.dachlatten.okhttp
+
+import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.Json
+import mockwebserver3.MockResponse
+import mockwebserver3.MockWebServer
+import mockwebserver3.junit5.internal.MockWebServerExtension
+import okhttp3.MediaType.Companion.toMediaType
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.ExtendWith
+import retrofit2.Call
+import retrofit2.Retrofit
+import retrofit2.http.Body
+import retrofit2.http.GET
+import retrofit2.http.POST
+
+@OptIn(ExperimentalSerializationApi::class)
+@ExtendWith(MockWebServerExtension::class)
+class KotlinSerializationConverterFactoryStringTest {
+    private lateinit var service: Service
+
+    interface Service {
+        @GET("/")
+        fun deserialize(): Call<User>
+        @POST("/")
+        fun serialize(@Body user: User): Call<Void?>
+    }
+
+    @Serializable
+    data class User(val name: String)
+
+    @BeforeEach
+    fun setUp(server: MockWebServer) {
+        val contentType = "application/json; charset=utf-8".toMediaType()
+        val retrofit = Retrofit.Builder()
+            .baseUrl(server.url("/"))
+            .addConverterFactory(Json.asConverterFactory(contentType))
+            .build()
+        service = retrofit.create(Service::class.java)
+    }
+
+    @Test
+    fun deserialize(server: MockWebServer) {
+        server.enqueue(MockResponse().newBuilder().body("""{"name":"Bob"}""").build())
+        val user = service.deserialize().execute().body()!!
+        assertEquals(User("Bob"), user)
+    }
+
+    @Test
+    fun serialize(server: MockWebServer) {
+        server.enqueue(MockResponse())
+        service.serialize(User("Bob")).execute()
+        val request = server.takeRequest()
+        assertEquals("""{"name":"Bob"}""", request.body.readUtf8())
+        assertEquals("application/json; charset=utf-8", request.headers["Content-Type"])
+    }
+}
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index f765183..f3d46db 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -12,9 +12,12 @@ robolectric = "4.10.3"
 compose = "1.5.4"
 compose-compiler = "1.5.7"
 kotlinx-datetime = "0.5.0"
+kotlinx-serialization = "1.6.2"
 kover = "0.7.5"
 mockk = "1.13.9"
 androidx-activity = "1.8.2"
+okhttp = "4.12.0"
+retrofit-serialization = "1.0.0"
 
 [libraries]
 coroutines = { group = "org.jetbrains.kotlinx", name = "kotlinx-coroutines-core", version.ref = "coroutines" }
@@ -35,15 +38,20 @@ kotlin-gradlePlugin = { group = "org.jetbrains.kotlin", name = "kotlin-gradle-pl
 kover-gradlePlugin = { group = "org.jetbrains.kotlinx.kover", name = "org.jetbrains.kotlinx.kover.gradle.plugin", version.ref = "kover" }
 annotation-jvm = { group = "androidx.annotation", name = "annotation-jvm", version.ref = "annotation-jvm" }
 kotlinx-datetime = { group = "org.jetbrains.kotlinx", name = "kotlinx-datetime-jvm", version.ref = "kotlinx-datetime" }
+kotlinx-serialization = { group = "org.jetbrains.kotlinx", name = "kotlinx-serialization-json", version.ref = "kotlinx-serialization" }
+okhttp = { group = "com.squareup.okhttp3", name = "okhttp", version.ref = "okhttp" }
+okhttp-mockwebserver = { group = "com.squareup.okhttp3", name = "mockwebserver3-junit5", version.prefer = "5.0.0-alpha.12" }
+retrofit-serialization = { group = "com.jakewharton.retrofit", name = "retrofit2-kotlinx-serialization-converter", version.ref = "retrofit-serialization" }
 
 mockk-agent = { group = "io.mockk", name = "mockk-agent", version.ref = "mockk" }
 mockk-jvm = { group = "io.mockk", name = "mockk-jvm", version.ref = "mockk" }
 
 [bundles]
 compose-ui-test = ["compose-ui-test-junit4", "compose-ui-test-manifest"]
-mockk =  ["mockk-agent", "mockk-jvm"]
+mockk = ["mockk-agent", "mockk-jvm"]
 
 [plugins]
 androidLibrary = { id = "com.android.library", version.ref = "agp" }
 kotlinAndroid = { id = "org.jetbrains.kotlin.android", version.ref = "kotlin" }
 koverPlugin = { id = "org.jetbrains.kotlinx.kover", version.ref = "kover" }
+kotlin-serialization-plugin = { id = "org.jetbrains.kotlin.plugin.serialization", version.ref = "kotlin" }
diff --git a/settings.gradle.kts b/settings.gradle.kts
index 4ebe18a..2743031 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -28,3 +28,4 @@ include(":dachlatten-debug")
 include(":dachlatten-flow")
 include(":dachlatten-google")
 include(":dachlatten-primitives")
+include(":dachlatten-retrofit")