diff --git a/app/src/main/java/tech/httptoolkit/android/HttpToolkitApplication.kt b/app/src/main/java/tech/httptoolkit/android/HttpToolkitApplication.kt
index 468d726..95a0241 100644
--- a/app/src/main/java/tech/httptoolkit/android/HttpToolkitApplication.kt
+++ b/app/src/main/java/tech/httptoolkit/android/HttpToolkitApplication.kt
@@ -26,6 +26,7 @@ private const val VPN_START_TIME_PREF = "vpn-start-time"
 private const val LAST_UPDATE_CHECK_TIME_PREF = "update-check-time"
 private const val APP_CRASHED_PREF = "app-crashed"
 private const val FIRST_RUN_PREF = "is-first-run"
+private const val SEEN_ANDROID_14_WARNING_PREF = "seen-android-14-warning"
 
 private val isProbablyEmulator =
         Build.FINGERPRINT.startsWith("generic")
@@ -96,6 +97,17 @@ class HttpToolkitApplication : Application() {
             }
     }
 
+    /**
+     * Check if the Android 14 warning has already been seen. This returns the value,
+     * and sets it to true if it was not already, so this will only return 'false'
+     * the first time it is ever called.
+     */
+    fun popAndroid14WarningState(): Boolean {
+        val hasSeenWarning = prefs.getBoolean(SEEN_ANDROID_14_WARNING_PREF, false)
+        prefs.edit().putBoolean(SEEN_ANDROID_14_WARNING_PREF, true).apply()
+        return hasSeenWarning
+    }
+
     /**
      * Grab any first run params, drop them for future usage, and return them.
      * This will return first-run params at most once (per install).
diff --git a/app/src/main/java/tech/httptoolkit/android/MainActivity.kt b/app/src/main/java/tech/httptoolkit/android/MainActivity.kt
index 074530e..e5d67dc 100644
--- a/app/src/main/java/tech/httptoolkit/android/MainActivity.kt
+++ b/app/src/main/java/tech/httptoolkit/android/MainActivity.kt
@@ -105,6 +105,17 @@ class MainActivity : AppCompatActivity(), CoroutineScope by MainScope() {
 
         Log.i(TAG, "Main activity created")
 
+        if (
+            // Should the real value later on
+            Build.VERSION.RELEASE == "14" ||
+            Build.VERSION.RELEASE == "15" || // Reasonable guess for the future
+            // Or, while it's still in beta:
+            Build.VERSION.RELEASE_OR_CODENAME == "UpsideDownCake"
+        ) {
+            val hasSeenWarningAlready = app.popAndroid14WarningState()
+            if (!hasSeenWarningAlready) showAndroid14Alert()
+        }
+
         // Are we being opened by an intent? I.e. a barcode scan/URL elsewhere on the device
         if (intent != null) {
             onNewIntent(intent)
@@ -937,6 +948,22 @@ class MainActivity : AppCompatActivity(), CoroutineScope by MainScope() {
             .show()
     }
 
+    private fun showAndroid14Alert() {
+        MaterialAlertDialogBuilder(this)
+            .setTitle("System interception is not available on Android 14+")
+            .setIcon(R.drawable.ic_exclamation_triangle)
+            .setMessage(
+                "Android 14 includes some changes which make system interception impossible." +
+                "\n\n" +
+                "This is a general issue that blocks system interception by HTTP Toolkit and all " +
+                "similar tools." +
+                "\n\n" +
+                "To use system interception, you will need to use Android 13 or older."
+            )
+            .setNeutralButton("Ok") { _, _ -> }
+            .show()
+    }
+
     private fun tryStartActivity(intent: Intent): Boolean {
         return try {
             startActivity(intent)