diff --git a/examples/TicTacToe/Systems/RenderSystem.cs b/examples/TicTacToe/Systems/RenderSystem.cs
index a20b454..ad061da 100644
--- a/examples/TicTacToe/Systems/RenderSystem.cs
+++ b/examples/TicTacToe/Systems/RenderSystem.cs
@@ -7,13 +7,6 @@ namespace TicTacToe;
 /// </summary>
 public class RenderSystem : ISystem
 {
-    public QueryDescriptor Query { get; }
-
-    public RenderSystem(World world)
-    {
-        Query = world.Query().With<Cell>().Build();
-    }
-
     public void Run(World world)
     {
         var state = world.ReadSingleton<GameState>();
@@ -66,4 +59,4 @@ public class RenderSystem : ISystem
         Console.WriteLine();
         Console.Write("  Enter row col (e.g. \"1 2\"): ");
     }
-}
+}
\ No newline at end of file
diff --git a/examples/TicTacToe/Systems/WinCheckSystem.cs b/examples/TicTacToe/Systems/WinCheckSystem.cs
index 185d2d1..cb56ec1 100644
--- a/examples/TicTacToe/Systems/WinCheckSystem.cs
+++ b/examples/TicTacToe/Systems/WinCheckSystem.cs
@@ -8,13 +8,6 @@ namespace TicTacToe;
 /// </summary>
 public class WinCheckSystem : ISystem
 {
-    public QueryDescriptor Query { get; }
-
-    public WinCheckSystem(World world)
-    {
-        Query = world.Query().With<Cell>().With<Mark>().Build();
-    }
-
     public void Run(World world)
     {
         ref var state = ref world.GetSingleton<GameState>();
@@ -25,7 +18,8 @@ public class WinCheckSystem : ISystem
         // Build a 3×3 grid of marks using the iterator API.
         var grid = new Player[3, 3];
 
-        using var iter = world.Select<Cell, Mark>(Query);
+        var query = world.Query().With<Cell>().With<Mark>().Build();
+        using var iter = world.Select<Cell, Mark>(query);
         while (iter.MoveNext())
         {
             grid[iter.Current1.Row, iter.Current1.Col] = iter.Current2.Player;
@@ -87,4 +81,4 @@ public class WinCheckSystem : ISystem
         state.Status = winner == Player.X ? GameStatus.XWon : GameStatus.OWon;
         world.MarkModified<GameState>(World.SingletonEntity);
     }
-}
+}
\ No newline at end of file
diff --git a/src/OECS/ISystem.cs b/src/OECS/ISystem.cs
index 0aab965..4ed3d14 100644
--- a/src/OECS/ISystem.cs
+++ b/src/OECS/ISystem.cs
@@ -2,15 +2,10 @@ namespace OECS;
 
 /// <summary>
 /// A system that runs on every tick.
-/// Systems declare a query and receive the world in their <see cref="Run"/> method.
+/// Systems receive the world in their <see cref="Run"/> method.
 /// </summary>
 public interface ISystem
 {
-    /// <summary>
-    /// The query that defines which entities this system operates on.
-    /// </summary>
-    QueryDescriptor Query { get; }
-
     /// <summary>
     /// Executes the system logic for this tick.
     /// </summary>
diff --git a/tests/OECS.Tests/CommandTests.cs b/tests/OECS.Tests/CommandTests.cs
index 2f55293..f5371a0 100644
--- a/tests/OECS.Tests/CommandTests.cs
+++ b/tests/OECS.Tests/CommandTests.cs
@@ -249,13 +249,10 @@ public class CommandTests
         private readonly World _world;
         private readonly SpawnCommand _command;
 
-        public QueryDescriptor Query { get; }
-
         public CommandEnqueueSystem(World world, SpawnCommand command)
         {
             _world = world;
             _command = command;
-            Query = world.Query().With<TestPosition>().Build();
         }
 
         public void Run(World world)
@@ -266,18 +263,17 @@ public class CommandTests
 
     private class EntityCountObserver : ISystem
     {
+        private readonly QueryDescriptor _query;
         public int SeenCount { get; private set; }
 
-        public QueryDescriptor Query { get; }
-
         public EntityCountObserver(World world)
         {
-            Query = world.Query().With<TestPosition>().Build();
+            _query = world.Query().With<TestPosition>().Build();
         }
 
         public void Run(World world)
         {
-            world.ForEach(Query, (Entity e, ref TestPosition pos) =>
+            world.ForEach(_query, (Entity e, ref TestPosition pos) =>
             {
                 SeenCount++;
             });
diff --git a/tests/OECS.Tests/QueryAndSystemTests.cs b/tests/OECS.Tests/QueryAndSystemTests.cs
index 832273f..eb437d0 100644
--- a/tests/OECS.Tests/QueryAndSystemTests.cs
+++ b/tests/OECS.Tests/QueryAndSystemTests.cs
@@ -175,11 +175,11 @@ public class SystemTests
 
     private class MovementSystem : ITickedSystem
     {
-        public QueryDescriptor Query { get; }
+        private readonly QueryDescriptor _query;
 
         public MovementSystem(World world)
         {
-            Query = world.Query().With<Position>().With<Velocity>().Build();
+            _query = world.Query().With<Position>().With<Velocity>().Build();
         }
 
         public void Run(World world) => Run(world, Tick.Logical());
@@ -187,7 +187,7 @@ public class SystemTests
         public void Run(World world, Tick tick)
         {
             float dt = tick.DeltaTime;
-            world.ForEach(Query, (Entity entity, ref Position pos, ref Velocity vel) =>
+            world.ForEach(_query, (Entity entity, ref Position pos, ref Velocity vel) =>
             {
                 pos.X += vel.X * dt;
                 pos.Y += vel.Y * dt;
@@ -232,13 +232,11 @@ public class SystemTests
 
     private class TestLogicalSystem : ITickedSystem
     {
-        public QueryDescriptor Query { get; }
         public bool WasCalled { get; private set; }
         public Tick ReceivedTick { get; private set; }
 
         public TestLogicalSystem(World world)
         {
-            Query = world.Query().With<Position>().Build();
         }
 
         public void Run(World world) => Run(world, Tick.Logical());
@@ -272,13 +270,10 @@ public class SystemTests
         private readonly int _id;
         private readonly List<int> _order;
 
-        public QueryDescriptor Query { get; }
-
         public OrderTrackingSystem(World world, int id, List<int> order)
         {
             _id = id;
             _order = order;
-            Query = world.Query().With<Position>().Build();
         }
 
         public void Run(World world)
diff --git a/tests/OECS.Tests/ReactivityTests.cs b/tests/OECS.Tests/ReactivityTests.cs
index 66eebe7..bae31be 100644
--- a/tests/OECS.Tests/ReactivityTests.cs
+++ b/tests/OECS.Tests/ReactivityTests.cs
@@ -268,12 +268,9 @@ public class ReactivityTests
     {
         private readonly World _world;
 
-        public QueryDescriptor Query { get; }
-
         public EntityCreatorSystem(World world)
         {
             _world = world;
-            Query = world.Query().With<Position>().Build();
         }
 
         public void Run(World world)
diff --git a/tests/OECS.Tests/SingletonTests.cs b/tests/OECS.Tests/SingletonTests.cs
index 11fc1c9..0e258c7 100644
--- a/tests/OECS.Tests/SingletonTests.cs
+++ b/tests/OECS.Tests/SingletonTests.cs
@@ -148,12 +148,9 @@ public class SingletonTests
     {
         private readonly World _world;
 
-        public QueryDescriptor Query { get; }
-
         public TimeSystem(World world)
         {
             _world = world;
-            Query = world.Query().With<GameConfig>().Build();
         }
 
         public void Run(World world) => Run(world, Tick.Logical());