diff --git a/Harmony/Public/Harmony.cs b/Harmony/Public/Harmony.cs
index 5784913e..5788d896 100644
--- a/Harmony/Public/Harmony.cs
+++ b/Harmony/Public/Harmony.cs
@@ -3,6 +3,7 @@
 using System.Diagnostics;
 using System.Linq;
 using System.Reflection;
+using System.Runtime.CompilerServices;
 
 namespace HarmonyLib
 {
@@ -132,21 +133,41 @@ public void PatchCategory(string category)
 			PatchCategory(assembly, category);
 		}
 
+		private static readonly ConditionalWeakTable<Assembly, Dictionary<string, List<Type>>> AssemblyCachedCategories = new();
+
 		/// <summary>Searches an assembly for HarmonyPatch-annotated classes/structs with a specific category and uses them to create patches</summary>
 		/// <param name="assembly">The assembly</param>
 		/// <param name="category">Name of patch category</param>
 		///
 		public void PatchCategory(Assembly assembly, string category)
 		{
-			AccessTools.GetTypesFromAssembly(assembly)
-				.Where(type =>
+			var categoryCache = AssemblyCachedCategories.GetValue(assembly, BuildCategoryCache);
+			if (categoryCache.TryGetValue(category, out var toPatch))
+			{
+				toPatch.Do(type => CreateClassProcessor(type).Patch());
+			}
+		}
+
+		private static Dictionary<string, List<Type>> BuildCategoryCache(Assembly assembly)
+		{
+			Dictionary<string, List<Type>> toBuild = [];
+			foreach (var type in AccessTools.GetTypesFromAssembly(assembly))
+			{
+				var harmonyAttributes = HarmonyMethodExtensions.GetFromType(type);
+				if (harmonyAttributes.Count == 0) continue;
+				var containerAttributes = HarmonyMethod.Merge(harmonyAttributes);
+				var category = containerAttributes.category;
+				if (!string.IsNullOrEmpty(category))
 				{
-					var harmonyAttributes = HarmonyMethodExtensions.GetFromType(type);
-					if (harmonyAttributes.Count == 0) return false;
-					var containerAttributes = HarmonyMethod.Merge(harmonyAttributes);
-					return containerAttributes.category == category;
-				})
-				.Do(type => CreateClassProcessor(type).Patch());
+					if (!toBuild.TryGetValue(category, out var typeList))
+					{
+						typeList ??= [];
+					}
+					typeList.Add(type);
+					toBuild[category] = typeList;
+				}
+			}
+			return toBuild;
 		}
 
 		/// <summary>Creates patches by manually specifying the methods</summary>
@@ -239,15 +260,11 @@ public void UnpatchCategory(string category)
 		///
 		public void UnpatchCategory(Assembly assembly, string category)
 		{
-			AccessTools.GetTypesFromAssembly(assembly)
-				.Where(type =>
-				{
-					var harmonyAttributes = HarmonyMethodExtensions.GetFromType(type);
-					if (harmonyAttributes.Count == 0) return false;
-					var containerAttributes = HarmonyMethod.Merge(harmonyAttributes);
-					return containerAttributes.category == category;
-				})
-				.Do(type => CreateClassProcessor(type).Unpatch());
+			var categoryCache = AssemblyCachedCategories.GetValue(assembly, BuildCategoryCache);
+			if (categoryCache.TryGetValue(category, out var toPatch))
+			{
+				toPatch.Do(type => CreateClassProcessor(type).Unpatch());
+			}
 		}
 
 		/// <summary>Test for patches from a specific Harmony ID</summary>
diff --git a/HarmonyTests/Patching/CategoryPatches.cs b/HarmonyTests/Patching/CategoryPatches.cs
new file mode 100644
index 00000000..9b101391
--- /dev/null
+++ b/HarmonyTests/Patching/CategoryPatches.cs
@@ -0,0 +1,89 @@
+using HarmonyLib;
+using NUnit.Framework;
+using System.Runtime.CompilerServices;
+
+namespace HarmonyLibTests.Patching
+{
+	[TestFixture, NonParallelizable]
+	public class CategoryPatches : TestLogger
+	{
+		[Test]
+		public void Test_HarmonyPatchAll()
+		{
+			var harmony = new Harmony("test");
+			harmony.PatchCategory("CategoryA");
+
+			Assert.AreEqual(2, Get1());
+			Assert.AreEqual(false, GetTrue());
+			Assert.AreEqual("Hello World", GetHelloWorld());
+			Assert.AreEqual(18, Multiply(3, 6));
+
+
+			harmony.PatchCategory("CategoryB");
+
+			Assert.AreEqual(2, Get1());
+			Assert.AreEqual(false, GetTrue());
+			Assert.AreEqual("Hello World!", GetHelloWorld());
+			Assert.AreEqual(36, Multiply(3, 6));
+
+			harmony.UnpatchCategory("CategoryA");
+
+			Assert.AreEqual(1, Get1());
+			Assert.AreEqual(true, GetTrue());
+			Assert.AreEqual("Hello World!", GetHelloWorld());
+			Assert.AreEqual(36, Multiply(3, 6));
+
+			harmony.UnpatchCategory("CategoryB");
+
+			Assert.AreEqual(1, Get1());
+			Assert.AreEqual(true, GetTrue());
+			Assert.AreEqual("Hello World", GetHelloWorld());
+			Assert.AreEqual(18, Multiply(3, 6));
+		}
+		[MethodImpl(MethodImplOptions.NoInlining)]
+		public static int Get1() => 1;
+
+		[MethodImpl(MethodImplOptions.NoInlining)]
+		public static bool GetTrue() => true;
+
+		[MethodImpl(MethodImplOptions.NoInlining)]
+		public static string GetHelloWorld() => "Hello World";
+
+		[MethodImpl(MethodImplOptions.NoInlining)]
+		public static int Multiply(int a, int b) => a * b;
+
+		[HarmonyPatch]
+		[HarmonyPatch(typeof(CategoryPatches))]
+		[HarmonyPatchCategory("CategoryA")]
+		static class CategoryAPatches
+		{
+			[HarmonyPatch(nameof(Get1)), HarmonyPrefix]
+			public static bool Get1Patch(ref int __result)
+			{
+				__result = 2;
+				return false;
+			}
+			[HarmonyPatch(nameof(GetTrue)), HarmonyPostfix]
+			public static void GetTruePatch(ref bool __result)
+			{
+				__result = false;
+			}
+		}
+
+		[HarmonyPatch]
+		[HarmonyPatchCategory("CategoryB")]
+		static class CategoryBPatches
+		{
+			[HarmonyPatch(typeof(CategoryPatches), nameof(GetHelloWorld)), HarmonyPostfix]
+			public static void GetHelloWorldPatch(ref string __result)
+			{
+				__result = __result + "!";
+			}
+			[HarmonyPatch(typeof(CategoryPatches), nameof(Multiply)), HarmonyPrefix]
+			public static void Multiply(ref int a)
+			{
+				a *= 2;
+			}
+		}
+	}
+}