diff --git a/src/Turnierplan.ImageStorage.Test.Integration/S3/S3ImageStorageTest.cs b/src/Turnierplan.ImageStorage.Test.Integration/S3/S3ImageStorageTest.cs
new file mode 100644
index 00000000..e7d3b175
--- /dev/null
+++ b/src/Turnierplan.ImageStorage.Test.Integration/S3/S3ImageStorageTest.cs
@@ -0,0 +1,266 @@
+using Amazon.S3;
+using FluentAssertions;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using S3ServerLibrary;
+using S3ServerLibrary.S3Objects;
+using Turnierplan.Core.Image;
+using Turnierplan.Core.PublicId;
+using Turnierplan.ImageStorage.S3;
+using WatsonWebserver.Core;
+using Xunit;
+using BindingFlags = System.Reflection.BindingFlags;
+
+namespace Turnierplan.ImageStorage.Test.Integration.S3;
+
+public sealed class S3ImageStorageTest : IDisposable
+{
+    private readonly int _port;
+    private readonly S3Server _server;
+    private readonly S3ImageStorageOptions _options;
+    private readonly TestLogger _logger;
+
+    public S3ImageStorageTest(ITestOutputHelper testOutputHelper)
+    {
+        _port = Random.Shared.Next(50000, 51000);
+
+        var settings = new S3ServerSettings
+        {
+            Webserver = new WebserverSettings("localhost", _port),
+            Logger = testOutputHelper.WriteLine
+        };
+
+        _options = new S3ImageStorageOptions
+        {
+            ServiceUrl = $"http://localhost:{_port}",
+            AccessKey = "key",
+            AccessKeySecret = "s3cr3t",
+            BucketName = "test_bucket"
+        };
+
+        _server = new S3Server(settings);
+        _server.Start();
+
+        _logger = new TestLogger();
+    }
+
+    public void Dispose()
+    {
+        _server.Dispose();
+    }
+
+    [Fact]
+    public void S3ImageStorage_Throws_Exception_When_Both_ServiceUrl_And_RegionEndpoint_Are_Specified()
+    {
+        var invalidOptions = _options with { RegionEndpoint = "us-east-1" };
+        var action = () => new S3ImageStorage(new OptionsWrapper<S3ImageStorageOptions>(invalidOptions), _logger);
+        action.Should().ThrowExactly<InvalidOperationException>().WithMessage("Please specify either 'RegionEndpoint' or 'ServiceUrl'.");
+    }
+
+    [Fact]
+    public void S3ImageStorage_Throws_Exception_When_Invalid_RegionEndpoint_Is_Specified()
+    {
+        var invalidOptions = _options with { RegionEndpoint = "test" };
+        var action = () => new S3ImageStorage(new OptionsWrapper<S3ImageStorageOptions>(invalidOptions), _logger);
+        action.Should().ThrowExactly<InvalidOperationException>().WithMessage("The specified region endpoint 'test' seems to be unknown.");
+    }
+
+    [Fact]
+    public void S3ImageStorage_GetFullImageUrl_Returns_Correct_Value()
+    {
+        using var storage = new S3ImageStorage(new OptionsWrapper<S3ImageStorageOptions>(_options), _logger);
+
+        var image = CreateImage(Guid.Parse("969bd4c6-c7bb-4631-8c25-1e196bc77512"), new DateTime(2026, 7, 27), "png");
+        storage.GetFullImageUrl(image).Should().Be($"http://localhost:{_port}/images/2026/07/969bd4c6-c7bb-4631-8c25-1e196bc77512.png");
+
+        var image2 = CreateImage(Guid.Parse("88a530a9-0272-4b2d-a495-b876ba30b005"), new DateTime(2025, 12, 27), "jpeg");
+        storage.GetFullImageUrl(image2).Should().Be($"http://localhost:{_port}/images/2025/12/88a530a9-0272-4b2d-a495-b876ba30b005.jpeg");
+
+        var awsOptions = _options with { ServiceUrl = null, RegionEndpoint = "us-east-1" };
+        using var awsStorage = new S3ImageStorage(new OptionsWrapper<S3ImageStorageOptions>(awsOptions), _logger);
+
+        awsStorage.GetFullImageUrl(image).Should().Be("https://test_bucket.s3.us-east-1.amazonaws.com/images/2026/07/969bd4c6-c7bb-4631-8c25-1e196bc77512.png");
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public async Task S3ImageStorage_With_Local_Server_Can_Upload_Image(bool isAuthenticated)
+    {
+        using var storage = new S3ImageStorage(new OptionsWrapper<S3ImageStorageOptions>(_options), _logger);
+
+        var image = CreateImage(Guid.Parse("969bd4c6-c7bb-4631-8c25-1e196bc77512"), new DateTime(2026, 7, 27), "png");
+        var imageData = new MemoryStream([0x00, 0x01, 0x02, 0x03]);
+
+        var writeCalled = false;
+        _server.Object.Write = async ctx =>
+        {
+            writeCalled = true;
+
+            if (!isAuthenticated)
+            {
+                ctx.Response.StatusCode = 401;
+                await ctx.Response.Send(ErrorCode.AccessDenied);
+            }
+
+            ctx.Request.Bucket.Should().Be("test_bucket");
+            ctx.Request.Key.Should().Be("images/2026/07/969bd4c6-c7bb-4631-8c25-1e196bc77512.png");
+        };
+
+        writeCalled.Should().BeFalse();
+        var result = await storage.SaveImageAsync(image, imageData);
+        writeCalled.Should().BeTrue();
+
+        if (isAuthenticated)
+        {
+            result.Should().BeTrue();
+            _logger.Messages.Should().BeEmpty();
+        }
+        else
+        {
+            result.Should().BeFalse();
+            _logger.Messages.Single().Should().Be("Failed to upload image 'images/2026/07/969bd4c6-c7bb-4631-8c25-1e196bc77512.png' to S3 because of an exception.");
+        }
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public async Task S3ImageStorage_With_Local_Server_Can_Read_Image(bool isAuthenticated)
+    {
+        using var storage = new S3ImageStorage(new OptionsWrapper<S3ImageStorageOptions>(_options), _logger);
+
+        var image = CreateImage(Guid.Parse("969bd4c6-c7bb-4631-8c25-1e196bc77512"), new DateTime(2026, 7, 27), "png");
+
+        var readCalled = false;
+        _server.Object.Read = async ctx =>
+        {
+            readCalled = true;
+
+            if (!isAuthenticated)
+            {
+                ctx.Response.StatusCode = 401;
+                await ctx.Response.Send(ErrorCode.AccessDenied);
+            }
+
+            ctx.Request.Bucket.Should().Be("test_bucket");
+            ctx.Request.Key.Should().Be("images/2026/07/969bd4c6-c7bb-4631-8c25-1e196bc77512.png");
+
+            var data = "Hello, S3!"u8;
+
+            return new S3Object(
+                ctx.Request.Key,
+                "version-1",
+                true,
+                DateTime.UtcNow,
+                "etag-123",
+                data.Length,
+                new Owner("admin", "Administrator"),
+                [.. data],
+                "text/plain"
+            );
+        };
+
+        readCalled.Should().BeFalse();
+
+        if (!isAuthenticated)
+        {
+            var func = () => storage.GetImageAsync(image);
+            await func.Should().ThrowAsync<AmazonS3Exception>().WithMessage("Access denied.");
+            readCalled.Should().BeTrue();
+
+            return;
+        }
+
+        await using var result = await storage.GetImageAsync(image);
+        readCalled.Should().BeTrue();
+
+        using var temp = new MemoryStream();
+        await result.CopyToAsync(temp, TestContext.Current.CancellationToken);
+
+        temp.ToArray().Should().BeEquivalentTo([0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x2c, 0x20, 0x53, 0x33, 0x21], opt => opt.WithStrictOrdering());
+
+        if (isAuthenticated)
+        {
+            _logger.Messages.Should().BeEmpty();
+        }
+        else
+        {
+            _logger.Messages.Single().Should().Be("Failed to upload image 'images/2026/07/969bd4c6-c7bb-4631-8c25-1e196bc77512.png' to S3 because of an exception.");
+        }
+
+        readCalled.Should().BeTrue();
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public async Task S3ImageStorage_With_Local_Server_Can_Delete_Image(bool isAuthenticated)
+    {
+        using var storage = new S3ImageStorage(new OptionsWrapper<S3ImageStorageOptions>(_options), _logger);
+
+        var image = CreateImage(Guid.Parse("969bd4c6-c7bb-4631-8c25-1e196bc77512"), new DateTime(2026, 7, 27), "png");
+
+        var writeCalled = false;
+        _server.Object.Delete = async ctx =>
+        {
+            writeCalled = true;
+
+            if (!isAuthenticated)
+            {
+                ctx.Response.StatusCode = 401;
+                await ctx.Response.Send(ErrorCode.AccessDenied);
+            }
+
+            ctx.Request.Bucket.Should().Be("test_bucket");
+            ctx.Request.Key.Should().Be("images/2026/07/969bd4c6-c7bb-4631-8c25-1e196bc77512.png");
+        };
+
+        writeCalled.Should().BeFalse();
+        var result = await storage.DeleteImageAsync(image);
+        writeCalled.Should().BeTrue();
+
+        if (isAuthenticated)
+        {
+            result.Should().BeTrue();
+            _logger.Messages.Should().BeEmpty();
+        }
+        else
+        {
+            result.Should().BeFalse();
+            _logger.Messages.Single().Should().Be("Failed to delete image 'images/2026/07/969bd4c6-c7bb-4631-8c25-1e196bc77512.png' from S3 because of an exception.");
+        }
+    }
+
+    private static Image CreateImage(Guid resourceIdentifier, DateTime createdAt, string extension)
+    {
+        // Create instances of Image class using reflection so we can specify resourceIdentifier & createdAt via internal ctor.
+
+        var ctor = typeof(Image).GetConstructor(
+            BindingFlags.NonPublic | BindingFlags.Instance,
+            [typeof(long), typeof(Guid), typeof(PublicId), typeof(DateTime), typeof(string), typeof(string), typeof(long), typeof(ushort), typeof(ushort)]);
+
+        if (ctor is null)
+        {
+            throw new InvalidOperationException($"Could not find internal '{nameof(Image)}' constructor.");
+        }
+
+        var image = ctor.Invoke([0L, resourceIdentifier, PublicId.Empty, createdAt, string.Empty, extension, 0L, (ushort)0, (ushort)0]);
+
+        return image as Image ?? throw new InvalidOperationException($"Could not instantiate '{nameof(Image)}' using reflection.");
+    }
+
+    private sealed class TestLogger : ILogger<S3ImageStorage>
+    {
+        public readonly List<string> Messages = [];
+
+        public IDisposable BeginScope<TState>(TState state) where TState : notnull => throw new NotSupportedException();
+
+        public bool IsEnabled(LogLevel logLevel) => true;
+
+        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception, Func<TState, Exception?, string> formatter)
+        {
+            Messages.Add(formatter(state, exception));
+        }
+    }
+}
diff --git a/src/Turnierplan.ImageStorage.Test.Integration/Turnierplan.ImageStorage.Test.Integration.csproj b/src/Turnierplan.ImageStorage.Test.Integration/Turnierplan.ImageStorage.Test.Integration.csproj
new file mode 100644
index 00000000..b364e5b4
--- /dev/null
+++ b/src/Turnierplan.ImageStorage.Test.Integration/Turnierplan.ImageStorage.Test.Integration.csproj
@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <Import Project="../version.xml" />
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <Import Project="../Turnierplan.Test.Common.props" />
+
+  <ItemGroup>
+    <PackageReference Include="S3Server" Version="7.3.1" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Turnierplan.ImageStorage\Turnierplan.ImageStorage.csproj" />
+  </ItemGroup>
+</Project>
diff --git a/src/Turnierplan.ImageStorage/AssemblyInfo.cs b/src/Turnierplan.ImageStorage/AssemblyInfo.cs
index 3533c6d3..6a11713a 100644
--- a/src/Turnierplan.ImageStorage/AssemblyInfo.cs
+++ b/src/Turnierplan.ImageStorage/AssemblyInfo.cs
@@ -1,3 +1,7 @@
 using System.Runtime.CompilerServices;
 
 [assembly: InternalsVisibleTo("Turnierplan.ImageStorage.Test.Migration")]
+
+// TODO: Once the image storage projects are refactored, each implementation should have
+//       a testable public API and the following line should no longer be necessary.
+[assembly: InternalsVisibleTo("Turnierplan.ImageStorage.Test.Integration")]
diff --git a/src/Turnierplan.ImageStorage/S3/S3ImageStorage.cs b/src/Turnierplan.ImageStorage/S3/S3ImageStorage.cs
index 0c54c038..3afda7ad 100644
--- a/src/Turnierplan.ImageStorage/S3/S3ImageStorage.cs
+++ b/src/Turnierplan.ImageStorage/S3/S3ImageStorage.cs
@@ -14,6 +14,7 @@ internal sealed class S3ImageStorage : IImageStorage
     private readonly ILogger<S3ImageStorage> _logger;
     private readonly AmazonS3Client _client;
     private readonly string _bucketName;
+    private readonly string? _serviceUrl;
 
     public S3ImageStorage(IOptions<S3ImageStorageOptions> options, ILogger<S3ImageStorage> logger)
     {
@@ -49,6 +50,7 @@ public S3ImageStorage(IOptions<S3ImageStorageOptions> options, ILogger<S3ImageSt
             }
 
             s3Config.ServiceURL = options.Value.ServiceUrl;
+            _serviceUrl = s3Config.ServiceURL.TrimEnd('/');
         }
 
         _client = new AmazonS3Client(s3Credentials, s3Config);
@@ -59,9 +61,9 @@ public string GetFullImageUrl(Image image)
     {
         var objectKey = GetObjectKey(image);
 
-        return string.IsNullOrWhiteSpace(_client.Config.ServiceURL)
+        return string.IsNullOrWhiteSpace(_serviceUrl)
             ? $"https://{_bucketName}.s3.{_client.Config.RegionEndpoint.SystemName}.amazonaws.com/{objectKey}"
-            : $"{_client.Config.ServiceURL}/{objectKey}";
+            : $"{_serviceUrl}/{objectKey}";
     }
 
     public async Task<bool> SaveImageAsync(Image image, MemoryStream imageData)
diff --git a/src/Turnierplan.ImageStorage/Turnierplan.ImageStorage.csproj b/src/Turnierplan.ImageStorage/Turnierplan.ImageStorage.csproj
index 6dedb7c4..86ed04fe 100644
--- a/src/Turnierplan.ImageStorage/Turnierplan.ImageStorage.csproj
+++ b/src/Turnierplan.ImageStorage/Turnierplan.ImageStorage.csproj
@@ -12,7 +12,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="AWSSDK.S3" Version="3.7.511.8" />
+    <PackageReference Include="AWSSDK.S3" Version="4.0.101.5" />
     <PackageReference Include="Azure.Identity" Version="1.21.0" />
     <PackageReference Include="Azure.Storage.Blobs" Version="12.29.0" />
   </ItemGroup>
diff --git a/src/turnierplan.NET.slnx b/src/turnierplan.NET.slnx
index 31da8eed..a409a491 100644
--- a/src/turnierplan.NET.slnx
+++ b/src/turnierplan.NET.slnx
@@ -10,6 +10,7 @@
     <Project Path="Turnierplan.Core.Test.Regression/Turnierplan.Core.Test.Regression.csproj" />
     <Project Path="Turnierplan.Core.Test.Unit/Turnierplan.Core.Test.Unit.csproj" />
     <Project Path="Turnierplan.Dal.Test.Unit/Turnierplan.Dal.Test.Unit.csproj" />
+    <Project Path="Turnierplan.ImageStorage.Test.Integration/Turnierplan.ImageStorage.Test.Integration.csproj" />
     <Project Path="Turnierplan.ImageStorage.Test.Migration/Turnierplan.ImageStorage.Test.Migration.csproj" />
     <Project Path="Turnierplan.Localization.Test.Unit/Turnierplan.Localization.Test.Unit.csproj" />
     <Project Path="Turnierplan.PdfRendering.Test.Unit/Turnierplan.PdfRendering.Test.Unit.csproj" />