diff --git a/StarMap.API/README.md b/StarMap.API/README.md
index 0a90ade..41880b9 100644
--- a/StarMap.API/README.md
+++ b/StarMap.API/README.md
@@ -220,3 +220,31 @@ Methods marked with this attribute will be called after `KSA.Program.OnFrame` is
 [StarMapAfterOnFrame]
 public void ModMethod(double currentPlayerTime, double dtPlayer);
 ```
+
+#### StarMapAfterSave
+
+Namespace: `StarMap.API`  
+Assembly: `StarMap.API`  
+Target: Method
+
+Methods marked with this attribute will be called after KSA has written a save, with the directory
+it was written to. A mod that keeps per-save state can write its own file beside `universe.xml`.
+
+```csharp
+[StarMapAfterSave]
+public void ModMethod(System.IO.DirectoryInfo saveDirectory);
+```
+
+#### StarMapAfterLoad
+
+Namespace: `StarMap.API`  
+Assembly: `StarMap.API`  
+Target: Method
+
+Methods marked with this attribute will be called after KSA has loaded a save, with the directory
+it was read from.
+
+```csharp
+[StarMapAfterLoad]
+public void ModMethod(System.IO.DirectoryInfo saveDirectory);
+```
diff --git a/StarMap.API/SaveAttributes.cs b/StarMap.API/SaveAttributes.cs
new file mode 100644
index 0000000..6f8bb70
--- /dev/null
+++ b/StarMap.API/SaveAttributes.cs
@@ -0,0 +1,75 @@
+using System.IO;
+using System.Reflection;
+
+namespace StarMap.API
+{
+    /// <summary>
+    /// Methods marked with this attribute will be called after KSA has written a save.
+    /// </summary>
+    /// <remarks>
+    /// Methods using this attribute must match the following signature:
+    ///
+    /// <code>
+    /// public void MethodName(System.IO.DirectoryInfo saveDirectory);
+    /// </code>
+    ///
+    /// Parameter requirements:
+    /// <list type="bullet">
+    ///   <item>
+    ///     <description>
+    ///       <paramref name="saveDirectory"/> is the folder the save was written to.
+    ///     </description>
+    ///   </item>
+    /// </list>
+    ///
+    /// Requirements:
+    /// <list type="bullet">
+    ///   <item><description>Return type must be <see cref="void"/>.</description></item>
+    ///   <item><description>Method must be an instance method (non-static).</description></item>
+    /// </list>
+    /// </remarks>
+    public sealed class StarMapAfterSaveAttribute : StarMapMethodAttribute
+    {
+        public override bool IsValidSignature(MethodInfo method)
+        {
+            return method.ReturnType == typeof(void) &&
+                   method.GetParameters().Length == 1 &&
+                   method.GetParameters()[0].ParameterType == typeof(DirectoryInfo);
+        }
+    }
+
+    /// <summary>
+    /// Methods marked with this attribute will be called after KSA has loaded a save.
+    /// </summary>
+    /// <remarks>
+    /// Methods using this attribute must match the following signature:
+    ///
+    /// <code>
+    /// public void MethodName(System.IO.DirectoryInfo saveDirectory);
+    /// </code>
+    ///
+    /// Parameter requirements:
+    /// <list type="bullet">
+    ///   <item>
+    ///     <description>
+    ///       <paramref name="saveDirectory"/> is the folder the save was read from.
+    ///     </description>
+    ///   </item>
+    /// </list>
+    ///
+    /// Requirements:
+    /// <list type="bullet">
+    ///   <item><description>Return type must be <see cref="void"/>.</description></item>
+    ///   <item><description>Method must be an instance method (non-static).</description></item>
+    /// </list>
+    /// </remarks>
+    public sealed class StarMapAfterLoadAttribute : StarMapMethodAttribute
+    {
+        public override bool IsValidSignature(MethodInfo method)
+        {
+            return method.ReturnType == typeof(void) &&
+                   method.GetParameters().Length == 1 &&
+                   method.GetParameters()[0].ParameterType == typeof(DirectoryInfo);
+        }
+    }
+}
diff --git a/StarMap.Core/Patches/UniverseDataPatcher.cs b/StarMap.Core/Patches/UniverseDataPatcher.cs
new file mode 100644
index 0000000..4bae1ee
--- /dev/null
+++ b/StarMap.Core/Patches/UniverseDataPatcher.cs
@@ -0,0 +1,42 @@
+using System.IO;
+using HarmonyLib;
+using KSA;
+using StarMap.API;
+
+namespace StarMap.Core.Patches
+{
+    /// <summary>
+    /// Tells mods when a save is written or read, and which directory it is in.
+    /// </summary>
+    [HarmonyPatch(typeof(UniverseData))]
+    internal static class UniverseDataPatcher
+    {
+        private const string WriteToMethodName = "WriteTo";
+        private const string LoadFromMethodName = "LoadFrom";
+
+        // WriteTo is overloaded; the DirectoryInfo one is the save on disk.
+        [HarmonyPatch(WriteToMethodName, [typeof(DirectoryInfo)])]
+        [HarmonyPostfix]
+        public static void AfterWriteTo(DirectoryInfo directory)
+        {
+            var methods = StarMapCore.Instance?.Loader.ModRegistry.Get<StarMapAfterSaveAttribute>() ?? [];
+
+            foreach (var (_, @object, method) in methods)
+            {
+                method.Invoke(@object, [directory]);
+            }
+        }
+
+        [HarmonyPatch(LoadFromMethodName)]
+        [HarmonyPostfix]
+        public static void AfterLoadFrom(UncompressedSave uncompressedSave)
+        {
+            var methods = StarMapCore.Instance?.Loader.ModRegistry.Get<StarMapAfterLoadAttribute>() ?? [];
+
+            foreach (var (_, @object, method) in methods)
+            {
+                method.Invoke(@object, [uncompressedSave.Directory]);
+            }
+        }
+    }
+}