diff --git a/README.md b/README.md
index 85709c0..3481b22 100644
--- a/README.md
+++ b/README.md
@@ -29,6 +29,8 @@ Files and folders will be recursively add/removed to match the filesystem.
 
 `SolutionItems` folder will be created and populated if missing. The name can be customized with `--folder`.
 
+If there is only one `.sln` file in the current folder then the `--solution` argument can be omitted and it will automatically be found.
+
 ## License
 
 - [A-GPL v3](LICENSE)
diff --git a/src/CLI.cs b/src/CLI.cs
index 9f30a46..0ff8157 100644
--- a/src/CLI.cs
+++ b/src/CLI.cs
@@ -18,8 +18,8 @@ public CLI(IGuidGenerator guidGenerator)
 
 	private class Options
 	{
-		[Option('s', "solution", Required = true, HelpText = "path to .sln file to modify")]
-		public required string SlnPath { get; set; }
+		[Option('s', "solution", HelpText = "path to .sln file to modify")]
+		public string? SlnPath { get; set; }
 
 		[Option('f', "folder", Required = false, HelpText = "Solution folder to target")]
 		public string SlnFolder { get; set; } = "SolutionItems";
@@ -61,6 +61,9 @@ public int Run(string[] args)
 			Console.Error.WriteLine();
 			WriteUsage();
 			return 5;
+		} catch(MultipleSlnFilesFoundException ex) {
+			Console.Error.WriteLine(ex.Message);
+			return 6;
 		}
 
 		Console.Out.WriteLine("Sync completed.");
diff --git a/src/SlnSync.cs b/src/SlnSync.cs
index 42dacff..e01f088 100644
--- a/src/SlnSync.cs
+++ b/src/SlnSync.cs
@@ -18,8 +18,12 @@ public SlnSync() : this(new DefaultGuidGenerator())
 	/// <param name="slnPath">relative path to sln file to modify</param>
 	/// <param name="slnFolder"></param>
 	/// <param name="paths">list of paths to recursively add/update SolutionItems virtual folders with</param>
-	public void SyncSlnFile(string slnPath, string slnFolder, IEnumerable<string> paths)
+	public void SyncSlnFile(string? slnPath, string slnFolder, IEnumerable<string> paths)
 	{
+		if (slnPath is null)
+		{
+			slnPath = FindSlnFile();
+		}
 		if (!slnPath.EndsWith(".sln"))
 		{
 			throw new InvalidSlnPathException(slnPath);
@@ -106,6 +110,23 @@ private void SyncFolder(SolutionFolder parentFolder, DirectoryInfo directory, st
 		}
 	}
 
+	/// <summary>
+	/// search current folder for single .sln file and return it
+	/// throw if not found or more than one found
+	/// </summary>
+	/// <returns>sln file if found</returns>
+	/// <exception cref="SlnFileNotFoundException"></exception>
+	private static string FindSlnFile()
+	{
+		var slnFiles = Directory.GetFiles(Directory.GetCurrentDirectory(), "*.sln");
+		return slnFiles.Length switch
+		{
+			0 => throw new SlnFileNotFoundException("No .sln files found in current directory."),
+			> 1 => throw new MultipleSlnFilesFoundException("Multiple .sln files found in current directory. Specify one with --solution"),
+			_ => slnFiles[0],
+		};
+	}
+
 	private SolutionFolder FindOrCreateSolutionFolder(ICollection<IProject> solutionProjects,
 		string solutionFolderName)
 	{
@@ -126,6 +147,7 @@ private SolutionFolder FindOrCreateSolutionFolder(ICollection<IProject> solution
 }
 
 public class PathNotFoundException(string path) : Exception($"Path not found: '{path}'");
+public class MultipleSlnFilesFoundException(string message) : Exception(message: message);
 public class SlnFileNotFoundException(string path) : Exception($"Invalid .sln file '{path}' - File not found.");
 public class InvalidSlnPathException(string path) : Exception($"Invalid .sln file '{path}' - File must have .sln extension");
 public class EmptyPathListException() : Exception();
diff --git a/tests/IntegrationTests.cs b/tests/IntegrationTests.cs
index f9ccbf4..3f5fe5a 100644
--- a/tests/IntegrationTests.cs
+++ b/tests/IntegrationTests.cs
@@ -9,6 +9,7 @@ public class IntegrationTests
 	private const string TargetSlnFile = "target.sln";
 	private readonly CLI _cli;
 	private readonly string _testFolder;
+	private const int SuccessExitCode = 0;
 
 	private static readonly string[] GuidsToReturn =
 	[
@@ -58,7 +59,8 @@ public void AddsToBlankSln()
 		});
 
 		// Act
-		_cli.Run(["-s", TargetSlnFile, "root-file.txt", "subfolder"]);
+		_cli.Run(["-s", TargetSlnFile, "root-file.txt", "subfolder"])
+			.Should().Be(SuccessExitCode, because: "command should succeed");
 
 		// Assert
 		const string expected = @"
@@ -143,7 +145,8 @@ public void IgnoresExistingItems()
 		});
 
 		// Act
-		_cli.Run(["-s", TargetSlnFile, "root-file.txt", "subfolder"]);
+		_cli.Run(["-s", TargetSlnFile, "root-file.txt", "subfolder"])
+			.Should().Be(SuccessExitCode, because: "command should succeed");
 
 		// Assert
 		const string expected = @"
@@ -229,7 +232,8 @@ public void RemovesMissingFiles()
 		});
 
 		// Act
-		_cli.Run(["-s", TargetSlnFile, "root-file.txt", "subfolder"]);
+		_cli.Run(["-s", TargetSlnFile, "root-file.txt", "subfolder"])
+			.Should().Be(SuccessExitCode, because: "command should succeed");
 
 		// Assert
 		const string expected = @"
@@ -298,7 +302,8 @@ public void CustomFolderName()
 		});
 
 		// Act
-		_cli.Run(["-s", TargetSlnFile, "-f", "My Items", "root-file.txt", "subfolder"]);
+		_cli.Run(["-s", TargetSlnFile, "-f", "My Items", "root-file.txt", "subfolder"])
+			.Should().Be(SuccessExitCode, because: "command should succeed");
 
 		// Assert
 		const string expected = @"
@@ -366,7 +371,8 @@ public void PathSanitization()
 		});
 
 		// Act
-		_cli.Run(["-s", TargetSlnFile, "root-file.txt", "subfolder/"]);
+		_cli.Run(["-s", TargetSlnFile, "root-file.txt", "subfolder/"])
+			.Should().Be(SuccessExitCode, because: "command should succeed");
 
 		// Assert
 		const string expected = @"
@@ -431,7 +437,8 @@ public void AddsBOM()
 		});
 
 		// Act
-		_cli.Run(["-s", TargetSlnFile, "some-file.txt"]);
+		_cli.Run(["-s", TargetSlnFile, "some-file.txt"])
+			.Should().Be(SuccessExitCode, because: "command should succeed");
 
 		File.ReadAllText(Path.Combine(_testFolder, TargetSlnFile));
 
@@ -489,7 +496,8 @@ public void RemovesEmptyFolder()
 		});
 
 		// Act
-		_cli.Run(["-s", TargetSlnFile, "subfolder"]);
+		_cli.Run(["-s", TargetSlnFile, "subfolder"])
+			.Should().Be(SuccessExitCode, because: "command should succeed");
 
 		// Assert
 		const string expected = @"
@@ -526,6 +534,75 @@ public void RemovesEmptyFolder()
 		ModifiedSln().Should().Be(expected);
 	}
 
+
+	[Fact]
+	public void FindsSlnFile()
+	{
+		// Arrange
+		SetupSln(@"
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.0.31903.59
+MinimumVisualStudioVersion = 10.0.40219.1
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+EndGlobal
+");
+
+		SetupFilesystem(new[]
+		{
+			"a-file.txt",
+		});
+
+		// Act
+		_cli.Run(["a-file.txt"])
+			.Should().Be(SuccessExitCode, because: "command should succeed");
+
+		// Assert
+		const string expected = @"
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.0.31903.59
+MinimumVisualStudioVersion = 10.0.40219.1
+Project(""{2150E333-8FDC-42A3-9474-1A3956D46DE8}"") = ""SolutionItems"", ""SolutionItems"", ""{17591C35-3F90-4F4A-AA13-45CF8D824066}""
+	ProjectSection(SolutionItems) = preProject
+		a-file.txt = a-file.txt
+	EndProjectSection
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+EndGlobal
+";
+
+		File.WriteAllText(Path.Combine(_testFolder, "expected.sln"), expected); // for kdiff debugging
+
+		ModifiedSln().Should().Be(expected);
+	}
+
+	[Fact]
+	public void FindsSlnFileInSameFolder()
+	{
+		File.WriteAllText(Path.Combine(_testFolder, "solution1.sln"), "blank");
+		File.WriteAllText(Path.Combine(_testFolder, "solution2.sln"), "blank");
+		_cli.Run(["some-file.txt"])
+			.Should().Be(6, because: "two solution files exist and arguments didn't specify which to use");
+		// todo: assert message written to stderr
+	}
+
 	private string ModifiedSln() => File.ReadAllText(Path.Combine(_testFolder, TargetSlnFile));
 
 	private void SetupFilesystem(IEnumerable<string> paths)
@@ -549,7 +626,9 @@ private void SetupFile(string path)
 
 	private void SetupSln(string slnContents)
 	{
-		File.WriteAllText(Path.Combine(_testFolder, "original.sln"), slnContents);
+		var originalSlnFolder = Path.Combine(_testFolder, "original"); // put in subfolder to avoid sln detection finding it
+		Directory.CreateDirectory(originalSlnFolder);
+		File.WriteAllText(Path.Combine(originalSlnFolder, "original.sln"), slnContents);
 		File.WriteAllText(Path.Combine(_testFolder, TargetSlnFile), slnContents);
 	}
 }