diff --git a/plugins/TypeWhisper.Plugin.Soniox/SonioxPlugin.cs b/plugins/TypeWhisper.Plugin.Soniox/SonioxPlugin.cs
index a4530c24..c955f9a2 100644
--- a/plugins/TypeWhisper.Plugin.Soniox/SonioxPlugin.cs
+++ b/plugins/TypeWhisper.Plugin.Soniox/SonioxPlugin.cs
@@ -15,7 +15,8 @@ public sealed class SonioxPlugin : ITranscriptionEnginePlugin
 {
     internal const string DefaultModelId = "default";
 
-    private const string BaseUrl = "https://api.soniox.com";
+    internal const string DefaultRegionId = "us";
+    private const string RegionSettingKey = "region";
     private const string ApiKeySecretName = "api-key";
     private const string SonioxAsyncModelId = "stt-async-v4";
     private const int DefaultMaxPollAttempts = 3600;
@@ -34,6 +35,19 @@ public sealed class SonioxPlugin : ITranscriptionEnginePlugin
         },
     ];
 
+    // Soniox data residency: each region has its own domain and requires an API key from a
+    // project created in that region. https://soniox.com/docs/stt/data-residency
+    private static readonly IReadOnlyList<SonioxRegion> Regions =
+    [
+        new(DefaultRegionId, "United States", "https://api.soniox.com"),
+        new("eu", "European Union", "https://api.eu.soniox.com"),
+        new("jp", "Japan", "https://api.jp.soniox.com"),
+    ];
+
+    // Each auto-detect probe is bounded so an unreachable region fails fast rather than
+    // blocking the settings Test flow for the full HttpClient timeout.
+    private static readonly TimeSpan RegionProbeTimeout = TimeSpan.FromSeconds(10);
+
     private readonly HttpClient _httpClient;
     private readonly TimeSpan _pollDelay;
     private readonly int _maxPollAttempts;
@@ -42,6 +56,7 @@ public sealed class SonioxPlugin : ITranscriptionEnginePlugin
     private IPluginHostServices? _host;
     private string? _apiKey;
     private string _selectedModelId = DefaultModelId;
+    private string _region = DefaultRegionId;
 
     /// <summary>
     /// Initializes a new instance of the SonioxPlugin class.
@@ -64,6 +79,8 @@ internal SonioxPlugin(
         _maxPollAttempts = maxPollAttempts;
     }
 
+    private string BaseUrl => ResolveRegion(_region).BaseUrl;
+
     // ITypeWhisperPlugin
 
     /// <summary>
@@ -77,7 +94,7 @@ internal SonioxPlugin(
     /// <summary>
     /// Gets the plugin version reported to the host.
     /// </summary>
-    public string PluginVersion => "1.0.3";
+    public string PluginVersion => "1.0.4";
 
     /// <summary>
     /// Activates the plugin and loads any persisted configuration.
@@ -87,7 +104,8 @@ public async Task ActivateAsync(IPluginHostServices host)
         _host = host;
         _apiKey = NormalizeApiKey(await host.LoadSecretAsync(ApiKeySecretName));
         _selectedModelId = DefaultModelId;
-        host.Log(PluginLogLevel.Info, $"Activated (configured={IsConfigured})");
+        _region = NormalizeRegionId(host.GetSetting<string>(RegionSettingKey));
+        host.Log(PluginLogLevel.Info, $"Activated (configured={IsConfigured}, region={_region})");
     }
 
     /// <summary>
@@ -206,6 +224,55 @@ public async Task<PluginTranscriptionResult> TranscribeWithLanguageHintsAsync(
     internal string? ApiKey => _apiKey;
     internal IPluginLocalization? Loc => _host?.Localization;
 
+    internal static IReadOnlyList<SonioxRegion> AvailableRegions => Regions;
+
+    /// <summary>Gets the currently selected Soniox data-residency region id.</summary>
+    internal string RegionId => _region;
+
+    /// <summary>Persists the selected Soniox region. Unknown ids fall back to the default (US).</summary>
+    internal void SetRegion(string regionId)
+    {
+        var normalized = NormalizeRegionId(regionId);
+        if (string.Equals(_region, normalized, StringComparison.Ordinal))
+            return;
+
+        _region = normalized;
+        _host?.SetSetting(RegionSettingKey, normalized);
+    }
+
+    /// <summary>
+    /// Probes each regional endpoint with the key and returns the region id it authenticates
+    /// against, or null if none accept it. Region is bound to the key's project, not the
+    /// user's location, so probing detects the correct region reliably.
+    /// </summary>
+    internal async Task<string?> DetectRegionAsync(string apiKey, CancellationToken ct = default)
+    {
+        var normalized = NormalizeApiKey(apiKey);
+        if (normalized is null)
+            return null;
+
+        foreach (var region in Regions)
+        {
+            // Bound the probe so an unreachable region fails fast instead of blocking on the
+            // full HttpClient timeout; a probe timeout skips to the next region, while a real
+            // caller cancellation still propagates.
+            using var probeCts = CancellationTokenSource.CreateLinkedTokenSource(ct);
+            probeCts.CancelAfter(RegionProbeTimeout);
+
+            try
+            {
+                if (await ProbeModelsAsync(region.BaseUrl, normalized, probeCts.Token))
+                    return region.Id;
+            }
+            catch (OperationCanceledException) when (!ct.IsCancellationRequested)
+            {
+                // This region's probe timed out; try the next region.
+            }
+        }
+
+        return null;
+    }
+
     internal async Task SetApiKeyAsync(string apiKey)
     {
         var normalized = NormalizeApiKey(apiKey);
@@ -249,10 +316,15 @@ internal async Task<bool> ValidateApiKeyAsync(string apiKey, CancellationToken c
         if (normalized is null)
             return false;
 
+        return await ProbeModelsAsync(BaseUrl, normalized, ct);
+    }
+
+    private async Task<bool> ProbeModelsAsync(string baseUrl, string apiKey, CancellationToken ct)
+    {
         try
         {
-            using var request = new HttpRequestMessage(HttpMethod.Get, $"{BaseUrl}/v1/models");
-            AddAuthorization(request, normalized);
+            using var request = new HttpRequestMessage(HttpMethod.Get, $"{baseUrl}/v1/models");
+            AddAuthorization(request, apiKey);
             using var response = await _httpClient.SendAsync(request, ct);
             return response.IsSuccessStatusCode;
         }
@@ -653,6 +725,13 @@ private static string ExtractApiError(JsonElement root)
                 : trimmed;
     }
 
+    private static string NormalizeRegionId(string? regionId) => ResolveRegion(regionId).Id;
+
+    private static SonioxRegion ResolveRegion(string? regionId) =>
+        Regions.FirstOrDefault(region =>
+            string.Equals(region.Id, regionId?.Trim(), StringComparison.OrdinalIgnoreCase))
+        ?? Regions[0];
+
     private static string? GetString(JsonElement element, string propertyName) =>
         element.TryGetProperty(propertyName, out var property)
         && property.ValueKind == JsonValueKind.String
@@ -676,6 +755,9 @@ private static bool TryGetDouble(JsonElement element, string propertyName, out d
 
     private sealed record SonioxTimedToken(string Text, double Start, double End);
 
+    /// <summary>A Soniox data-residency region and its REST base URL.</summary>
+    internal sealed record SonioxRegion(string Id, string DisplayName, string BaseUrl);
+
     /// <summary>
     /// Releases resources held by the instance.
     /// </summary>
diff --git a/plugins/TypeWhisper.Plugin.Soniox/SonioxSettingsView.xaml b/plugins/TypeWhisper.Plugin.Soniox/SonioxSettingsView.xaml
index 8061c44b..90585a0e 100644
--- a/plugins/TypeWhisper.Plugin.Soniox/SonioxSettingsView.xaml
+++ b/plugins/TypeWhisper.Plugin.Soniox/SonioxSettingsView.xaml
@@ -12,6 +12,8 @@
             <Button Grid.Column="1" Margin="8,0,0,0" Padding="12,4"
                     Click="OnTestClick" x:Name="TestButton" />
         </Grid>
+        <TextBlock x:Name="RegionLabel" FontWeight="SemiBold" Margin="0,10,0,4" />
+        <ComboBox x:Name="RegionBox" SelectionChanged="OnRegionChanged" />
         <TextBlock x:Name="StatusText" Margin="0,4,0,0" FontSize="12" />
     </StackPanel>
 </UserControl>
diff --git a/plugins/TypeWhisper.Plugin.Soniox/SonioxSettingsView.xaml.cs b/plugins/TypeWhisper.Plugin.Soniox/SonioxSettingsView.xaml.cs
index 69a071b5..82975abb 100644
--- a/plugins/TypeWhisper.Plugin.Soniox/SonioxSettingsView.xaml.cs
+++ b/plugins/TypeWhisper.Plugin.Soniox/SonioxSettingsView.xaml.cs
@@ -15,6 +15,7 @@ public partial class SonioxSettingsView : UserControl
     private readonly SonioxPlugin _plugin;
     private CancellationTokenSource? _saveDebounceCts;
     private readonly bool _suppressPasswordChanged;
+    private bool _suppressRegionChanged;
 
     /// <summary>
     /// Initializes a new instance of the SonioxSettingsView class.
@@ -26,6 +27,13 @@ public SonioxSettingsView(SonioxPlugin plugin)
 
         ApiKeyLabel.Text = L("Settings.ApiKeyLabel");
         TestButton.Content = L("Settings.Test");
+        RegionLabel.Text = L("Settings.Region");
+
+        _suppressRegionChanged = true;
+        foreach (var region in SonioxPlugin.AvailableRegions)
+            RegionBox.Items.Add(new ComboBoxItem { Content = region.DisplayName, Tag = region.Id });
+        SelectRegionItem(plugin.RegionId);
+        _suppressRegionChanged = false;
 
         if (!string.IsNullOrEmpty(plugin.ApiKey))
         {
@@ -102,14 +110,27 @@ private async void OnTestClick(object sender, RoutedEventArgs e)
         }
 
         TestButton.IsEnabled = false;
+        RegionBox.IsEnabled = false;
+        ApiKeyBox.IsEnabled = false;
         StatusText.Text = L("Settings.Testing");
         StatusText.Foreground = Brushes.Gray;
 
         try
         {
-            var valid = await _plugin.ValidateApiKeyAsync(key);
-            StatusText.Text = valid ? L("Settings.ApiKeyValid") : L("Settings.ApiKeyInvalid");
-            StatusText.Foreground = valid ? Brushes.Green : Brushes.Red;
+            var detectedRegion = await _plugin.DetectRegionAsync(key);
+            if (detectedRegion is not null)
+            {
+                ApplyDetectedRegion(detectedRegion);
+                var displayName = SonioxPlugin.AvailableRegions
+                    .First(region => region.Id == detectedRegion).DisplayName;
+                StatusText.Text = L("Settings.ApiKeyValidRegion", displayName);
+                StatusText.Foreground = Brushes.Green;
+            }
+            else
+            {
+                StatusText.Text = L("Settings.ApiKeyInvalid");
+                StatusText.Foreground = Brushes.Red;
+            }
         }
         catch (OperationCanceledException ex)
         {
@@ -130,7 +151,41 @@ private async void OnTestClick(object sender, RoutedEventArgs e)
         finally
         {
             TestButton.IsEnabled = true;
+            RegionBox.IsEnabled = true;
+            ApiKeyBox.IsEnabled = true;
+        }
+    }
+
+    private void OnRegionChanged(object sender, SelectionChangedEventArgs e)
+    {
+        if (_suppressRegionChanged)
+            return;
+
+        if ((RegionBox.SelectedItem as ComboBoxItem)?.Tag is string regionId)
+            _plugin.SetRegion(regionId);
+    }
+
+    private void SelectRegionItem(string regionId)
+    {
+        foreach (var item in RegionBox.Items)
+        {
+            if (item is ComboBoxItem comboItem && comboItem.Tag as string == regionId)
+            {
+                RegionBox.SelectedItem = comboItem;
+                return;
+            }
         }
+
+        if (RegionBox.Items.Count > 0)
+            RegionBox.SelectedIndex = 0;
+    }
+
+    private void ApplyDetectedRegion(string regionId)
+    {
+        _suppressRegionChanged = true;
+        SelectRegionItem(regionId);
+        _suppressRegionChanged = false;
+        _plugin.SetRegion(regionId);
     }
 
     private void ShowError(Exception ex)
@@ -164,7 +219,9 @@ internal static string FormatFallbackText(string key, object[] args)
             "Settings.EnterApiKey" => "Enter an API key.",
             "Settings.Testing" => "Testing...",
             "Settings.ApiKeyValid" => "API key valid.",
+            "Settings.ApiKeyValidRegion" => "API key valid (region: {0}).",
             "Settings.ApiKeyInvalid" => "Invalid API key.",
+            "Settings.Region" => "Soniox region",
             "Settings.Error" => "Error",
             _ => key
         };
diff --git a/plugins/TypeWhisper.Plugin.Soniox/manifest.json b/plugins/TypeWhisper.Plugin.Soniox/manifest.json
index cacebcf0..64798886 100644
--- a/plugins/TypeWhisper.Plugin.Soniox/manifest.json
+++ b/plugins/TypeWhisper.Plugin.Soniox/manifest.json
@@ -1,7 +1,7 @@
 {
   "id": "com.typewhisper.soniox",
   "name": "Soniox",
-  "version": "1.0.3",
+  "version": "1.0.4",
   "author": "TypeWhisper",
   "description": "Soniox speech-to-text transcription engine",
   "category": "transcription",
diff --git a/tests/TypeWhisper.PluginSystem.Tests/SonioxPluginTests.cs b/tests/TypeWhisper.PluginSystem.Tests/SonioxPluginTests.cs
index 6c06adaa..8e27133c 100644
--- a/tests/TypeWhisper.PluginSystem.Tests/SonioxPluginTests.cs
+++ b/tests/TypeWhisper.PluginSystem.Tests/SonioxPluginTests.cs
@@ -26,8 +26,8 @@ public void PluginVersion_IsSonioxMarketplaceReleaseVersion()
         var manifest = LoadManifest();
         var sut = new SonioxPlugin();
 
-        Assert.Equal("1.0.3", manifest.GetProperty("version").GetString());
-        Assert.Equal("1.0.3", sut.PluginVersion);
+        Assert.Equal("1.0.4", manifest.GetProperty("version").GetString());
+        Assert.Equal("1.0.4", sut.PluginVersion);
     }
 
     [Fact]
@@ -130,6 +130,87 @@ public async Task ValidateApiKeyAsync_UsesModelsEndpointAndBearerHeader()
         Assert.True(await sut.ValidateApiKeyAsync(" probe-key "));
     }
 
+    [Fact]
+    public async Task ActivateAsync_UsesPersistedRegionEndpoint()
+    {
+        var handler = new CapturingHandler((request, _) =>
+        {
+            Assert.Equal("https://api.jp.soniox.com/v1/models", request.RequestUri?.ToString());
+            return JsonResponse("""{ "models": [] }""");
+        });
+
+        var host = new TestPluginHostServices();
+        host.SetSetting("region", "jp");
+        using var httpClient = new HttpClient(handler);
+        var sut = new SonioxPlugin(httpClient);
+        await sut.ActivateAsync(host);
+
+        Assert.Equal("jp", sut.RegionId);
+        Assert.True(await sut.ValidateApiKeyAsync("probe-key"));
+    }
+
+    [Fact]
+    public async Task ActivateAsync_FallsBackToUsForUnknownRegion()
+    {
+        var host = new TestPluginHostServices();
+        host.SetSetting("region", "mars");
+        var sut = new SonioxPlugin();
+        await sut.ActivateAsync(host);
+
+        Assert.Equal("us", sut.RegionId);
+    }
+
+    [Fact]
+    public async Task SetRegion_PersistsRegionAndSwitchesEndpoint()
+    {
+        var handler = new CapturingHandler((request, _) =>
+        {
+            Assert.Equal("https://api.eu.soniox.com/v1/models", request.RequestUri?.ToString());
+            return JsonResponse("""{ "models": [] }""");
+        });
+
+        var host = new TestPluginHostServices();
+        using var httpClient = new HttpClient(handler);
+        var sut = new SonioxPlugin(httpClient);
+        await sut.ActivateAsync(host);
+
+        sut.SetRegion("eu");
+
+        Assert.Equal("eu", sut.RegionId);
+        Assert.Equal("eu", host.GetSetting<string>("region"));
+        Assert.True(await sut.ValidateApiKeyAsync("probe-key"));
+    }
+
+    [Fact]
+    public async Task DetectRegionAsync_ReturnsRegionWhereKeyAuthenticates()
+    {
+        var handler = new CapturingHandler((request, _) =>
+            request.RequestUri?.ToString() == "https://api.jp.soniox.com/v1/models"
+                ? JsonResponse("""{ "models": [] }""")
+                : JsonResponse("""{ "error": "unauthorized" }""", HttpStatusCode.Unauthorized));
+
+        var host = new TestPluginHostServices();
+        using var httpClient = new HttpClient(handler);
+        var sut = new SonioxPlugin(httpClient);
+        await sut.ActivateAsync(host);
+
+        Assert.Equal("jp", await sut.DetectRegionAsync("probe-key"));
+    }
+
+    [Fact]
+    public async Task DetectRegionAsync_ReturnsNullWhenNoRegionAccepts()
+    {
+        var handler = new CapturingHandler((_, _) =>
+            JsonResponse("""{ "error": "unauthorized" }""", HttpStatusCode.Unauthorized));
+
+        var host = new TestPluginHostServices();
+        using var httpClient = new HttpClient(handler);
+        var sut = new SonioxPlugin(httpClient);
+        await sut.ActivateAsync(host);
+
+        Assert.Null(await sut.DetectRegionAsync("probe-key"));
+    }
+
     [Fact]
     public async Task TranscribeWithLanguageHintsAsync_PreservesOrderAndCleansUp()
     {