diff --git a/runelite-client/src/main/java/net/runelite/client/config/RuneLiteConfig.java b/runelite-client/src/main/java/net/runelite/client/config/RuneLiteConfig.java
index 98b65669eda..faa52b83130 100644
--- a/runelite-client/src/main/java/net/runelite/client/config/RuneLiteConfig.java
+++ b/runelite-client/src/main/java/net/runelite/client/config/RuneLiteConfig.java
@@ -133,6 +133,22 @@ default boolean enableCustomChrome()
 		return OSType.getOSType() == OSType.Windows;
 	}
 
+	@Range(
+		min = 10,
+		max = 100
+	)
+	@ConfigItem(
+		keyName = "uiWindowOpacity",
+		name = "Window opacity",
+		description = "Set the windows opacity.",
+		position = 16,
+		section = windowSettings
+	)
+	default int windowOpacity()
+	{
+		return 100;
+	}
+
 	@ConfigItem(
 		keyName = "gameAlwaysOnTop",
 		name = "Always on top",
diff --git a/runelite-client/src/main/java/net/runelite/client/ui/ClientUI.java b/runelite-client/src/main/java/net/runelite/client/ui/ClientUI.java
index f28a29fec9c..8eff248e553 100644
--- a/runelite-client/src/main/java/net/runelite/client/ui/ClientUI.java
+++ b/runelite-client/src/main/java/net/runelite/client/ui/ClientUI.java
@@ -1114,6 +1114,12 @@ private void updateFrameConfig(boolean updateResizable)
 			return;
 		}
 
+		if (frame.getGraphicsConfiguration().isTranslucencyCapable() &&
+			frame.getGraphicsConfiguration().getDevice().getFullScreenWindow() == null)
+		{
+			frame.setOpacity(((float) config.windowOpacity()) / 100.0f);
+		}
+
 		if (config.usernameInTitle() && (client instanceof Client))
 		{
 			final Player player = ((Client) client).getLocalPlayer();
diff --git a/runelite-client/src/main/java/net/runelite/client/ui/ContainableFrame.java b/runelite-client/src/main/java/net/runelite/client/ui/ContainableFrame.java
index 42a0f3a158b..c95b9648de8 100644
--- a/runelite-client/src/main/java/net/runelite/client/ui/ContainableFrame.java
+++ b/runelite-client/src/main/java/net/runelite/client/ui/ContainableFrame.java
@@ -27,6 +27,7 @@
 import com.formdev.flatlaf.ui.FlatNativeWindowsLibrary;
 import java.awt.Dimension;
 import java.awt.Frame;
+import java.awt.IllegalComponentStateException;
 import java.awt.Insets;
 import java.awt.Rectangle;
 import java.awt.geom.AffineTransform;
@@ -52,6 +53,7 @@ public enum Mode
 	private boolean rightSideSuction;
 	private boolean boundsOpSet;
 	private boolean scaleMinSize = false;
+	private boolean overrideUndecorated;
 
 	@Override
 	@SuppressWarnings("deprecation")
@@ -259,4 +261,30 @@ void updateContainsInScreen()
 			FlatNativeWindowsLibrary.setContainInScreen(this, containedInScreen == Mode.ALWAYS);
 		}
 	}
+
+	@Override
+	public void setOpacity(float opacity)
+	{
+		// JDK-6993784 requires the frame to be undecorated to apply opacity, but in practice it works on Windows regardless.
+		// Temporarily pretend to be an undecorated frame to satisfy Frame.setOpacity().
+		overrideUndecorated = true;
+		try
+		{
+			super.setOpacity(opacity);
+		}
+		catch (IllegalComponentStateException | UnsupportedOperationException | IllegalArgumentException ex)
+		{
+			log.warn("unable to set opacity {}", opacity, ex);
+		}
+		finally
+		{
+			overrideUndecorated = false;
+		}
+	}
+
+	@Override
+	public boolean isUndecorated()
+	{
+		return overrideUndecorated || super.isUndecorated();
+	}
 }