diff --git a/src/main/java/io/swagger/codegen/v3/generators/java/JavaClientCodegen.java b/src/main/java/io/swagger/codegen/v3/generators/java/JavaClientCodegen.java
index 0d8dcfafff..5edfed25d4 100644
--- a/src/main/java/io/swagger/codegen/v3/generators/java/JavaClientCodegen.java
+++ b/src/main/java/io/swagger/codegen/v3/generators/java/JavaClientCodegen.java
@@ -40,6 +40,7 @@ public class JavaClientCodegen extends AbstractJavaCodegen implements BeanValida
 
     public static final String USE_RX_JAVA = "useRxJava";
     public static final String USE_RX_JAVA2 = "useRxJava2";
+    public static final String USE_RX_JAVA3 = "useRxJava3";
     public static final String DO_NOT_USE_RX = "doNotUseRx";
     public static final String USE_PLAY_WS = "usePlayWS";
     public static final String PLAY_VERSION = "playVersion";
@@ -55,6 +56,7 @@ public class JavaClientCodegen extends AbstractJavaCodegen implements BeanValida
     protected String gradleWrapperPackage = "gradle.wrapper";
     protected boolean useRxJava = false;
     protected boolean useRxJava2 = false;
+    protected boolean useRxJava3 = false;
     protected boolean doNotUseRx = true; // backwards compatibility for swagger configs that specify neither rx1 nor rx2 (mustache does not allow for boolean operators so we need this extra field)
     protected boolean usePlayWS = false;
     protected String playVersion = PLAY_25;
@@ -76,6 +78,7 @@ public JavaClientCodegen() {
 
         cliOptions.add(CliOption.newBoolean(USE_RX_JAVA, "Whether to use the RxJava adapter with the retrofit2 library."));
         cliOptions.add(CliOption.newBoolean(USE_RX_JAVA2, "Whether to use the RxJava2 adapter with the retrofit2 library."));
+        cliOptions.add(CliOption.newBoolean(USE_RX_JAVA3, "Whether to use the RxJava3 adapter with the retrofit2 library."));
         cliOptions.add(CliOption.newBoolean(PARCELABLE_MODEL, "Whether to generate models for Android that implement Parcelable with the okhttp-gson library."));
         cliOptions.add(CliOption.newBoolean(USE_PLAY_WS, "Use Play! Async HTTP client (Play WS API)"));
         cliOptions.add(CliOption.newString(PLAY_VERSION, "Version of Play! Framework (possible values \"play24\", \"play25\")"));
@@ -122,15 +125,17 @@ public String getHelp() {
     public void processOpts() {
         super.processOpts();
 
-        if (additionalProperties.containsKey(USE_RX_JAVA) && additionalProperties.containsKey(USE_RX_JAVA2)) {
-            LOGGER.warn("You specified both RxJava versions 1 and 2 but they are mutually exclusive. Defaulting to v2.");
-        } else if (additionalProperties.containsKey(USE_RX_JAVA)) {
+        if (additionalProperties.containsKey(USE_RX_JAVA)) {
             this.setUseRxJava(Boolean.valueOf(additionalProperties.get(USE_RX_JAVA).toString()));
         }
         if (additionalProperties.containsKey(USE_RX_JAVA2)) {
             this.setUseRxJava2(Boolean.valueOf(additionalProperties.get(USE_RX_JAVA2).toString()));
         }
-        if (!useRxJava && !useRxJava2) {
+        if (additionalProperties.containsKey(USE_RX_JAVA3)) {
+            this.setUseRxJava3(Boolean.valueOf(additionalProperties.get(USE_RX_JAVA3).toString()));
+        }
+
+        if (!useRxJava && !useRxJava2 && !useRxJava3) {
             additionalProperties.put(DO_NOT_USE_RX, true);
         }
         if (additionalProperties.containsKey(USE_PLAY_WS)) {
@@ -553,6 +558,11 @@ public void setUseRxJava2(boolean useRxJava2) {
         doNotUseRx = false;
     }
 
+    public void setUseRxJava3(boolean useRxJava3) {
+        this.useRxJava3 = useRxJava3;
+        doNotUseRx = false;
+    }
+
     public void setDoNotUseRx(boolean doNotUseRx) {
         this.doNotUseRx = doNotUseRx;
     }
diff --git a/src/main/resources/handlebars/Java/libraries/retrofit2/ApiClient.mustache b/src/main/resources/handlebars/Java/libraries/retrofit2/ApiClient.mustache
index 8e81e572cd..c8b53f5a1c 100644
--- a/src/main/resources/handlebars/Java/libraries/retrofit2/ApiClient.mustache
+++ b/src/main/resources/handlebars/Java/libraries/retrofit2/ApiClient.mustache
@@ -23,6 +23,9 @@ import retrofit2.adapter.rxjava.RxJavaCallAdapterFactory;
 {{#useRxJava2}}
 import retrofit2.adapter.rxjava2.RxJava2CallAdapterFactory;
 {{/useRxJava2}}
+{{#useRxJava3}}
+import hu.akarnokd.rxjava3.retrofit.RxJava3CallAdapterFactory;
+{{/useRxJava3}}
 import retrofit2.converter.gson.GsonConverterFactory;
 import retrofit2.converter.scalars.ScalarsConverterFactory;
 import {{invokerPackage}}.auth.HttpBasicAuth;
@@ -142,7 +145,9 @@ public class ApiClient {
       .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
       {{/useRxJava}}{{#useRxJava2}}
       .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
-      {{/useRxJava2}}
+      {{/useRxJava2}}{{#useRxJava3}}
+      .addCallAdapterFactory(RxJava3CallAdapterFactory.create())
+      {{/useRxJava3}}
       .addConverterFactory(ScalarsConverterFactory.create())
       .addConverterFactory(GsonCustomConverterFactory.create(json.getGson()));
   }
diff --git a/src/main/resources/handlebars/Java/libraries/retrofit2/api.mustache b/src/main/resources/handlebars/Java/libraries/retrofit2/api.mustache
index ccfe0df071..2d9dfc3517 100644
--- a/src/main/resources/handlebars/Java/libraries/retrofit2/api.mustache
+++ b/src/main/resources/handlebars/Java/libraries/retrofit2/api.mustache
@@ -8,6 +8,9 @@ import rx.Observable;
 {{#useRxJava2}}
 import io.reactivex.Observable;
 {{/useRxJava2}}
+{{#useRxJava3}}
+import io.reactivex.rxjava3.core.Observable;
+{{/useRxJava3}}
 {{#doNotUseRx}}
 import retrofit2.Call;
 {{/doNotUseRx}}
diff --git a/src/main/resources/handlebars/Java/libraries/retrofit2/pom.mustache b/src/main/resources/handlebars/Java/libraries/retrofit2/pom.mustache
index 828fd892da..a9da7810fe 100644
--- a/src/main/resources/handlebars/Java/libraries/retrofit2/pom.mustache
+++ b/src/main/resources/handlebars/Java/libraries/retrofit2/pom.mustache
@@ -246,6 +246,18 @@
       <version>${retrofit-version}</version>
     </dependency>
     {{/useRxJava2}}
+    {{#useRxJava3}}
+      <dependency>
+          <groupId>io.reactivex.rxjava3</groupId>
+          <artifactId>rxjava</artifactId>
+          <version>${rxjava-version}</version>
+      </dependency>
+      <dependency>
+          <groupId>com.github.akarnokd</groupId>
+          <artifactId>rxjava3-retrofit-adapter</artifactId>
+          <version>3.0.0</version>
+      </dependency>
+    {{/useRxJava3}}
 
     {{#usePlayWS}}
     <!-- JSON processing: jackson -->