diff --git a/README.md b/README.md
index cac8cf2..7b31031 100644
--- a/README.md
+++ b/README.md
@@ -211,7 +211,8 @@ The `TaskSeq` project already has a wide array of functions and functionalities,
   - [ ] `average` / `averageBy`, `sum` and related
   - [x] `forall` / `forallAsync` (see [#240])
   - [x] `skip` / `drop` / `truncate` / `take` (see [#209])
-  - [ ] `chunkBySize` / `windowed`
+  - [x] `chunkBySize` (see [#265])
+  - [ ] `windowed`
   - [ ] `compareWith`
   - [ ] `distinct`
   - [ ] `exists2` / `map2` / `fold2` / `iter2` and related '2'-functions
@@ -263,7 +264,7 @@ This is what has been implemented so far, is planned or skipped:
 | ✅ [#67][] |                    |                      | `box`                     | |
 | ✅ [#67][] |                    |                      | `unbox`                   | |
 | ✅ [#23][] | `choose`           | `choose`             | `chooseAsync`             | |
-|                  | `chunkBySize`      | `chunkBySize`        |                           | |
+| ✅ [#265][]| `chunkBySize`      | `chunkBySize`        |                           | |
 | ✅ [#11][] | `collect`          | `collect`            | `collectAsync`            | |
 | ✅ [#11][] |                    | `collectSeq`         | `collectSeqAsync`         | |
 |                  | `compareWith`      | `compareWith`        | `compareWithAsync`        | |
diff --git a/src/FSharp.Control.TaskSeq.Test/FSharp.Control.TaskSeq.Test.fsproj b/src/FSharp.Control.TaskSeq.Test/FSharp.Control.TaskSeq.Test.fsproj
index dbf1cfc..421459d 100644
--- a/src/FSharp.Control.TaskSeq.Test/FSharp.Control.TaskSeq.Test.fsproj
+++ b/src/FSharp.Control.TaskSeq.Test/FSharp.Control.TaskSeq.Test.fsproj
@@ -57,6 +57,7 @@
     <Compile Include="TaskSeq.Do.Tests.fs" />
     <Compile Include="TaskSeq.Let.Tests.fs" />
     <Compile Include="TaskSeq.Using.Tests.fs" />
+    <Compile Include="TaskSeq.ChunkBySize.Tests.fs" />
   </ItemGroup>
 
   <ItemGroup>
diff --git a/src/FSharp.Control.TaskSeq.Test/TaskSeq.ChunkBySize.Tests.fs b/src/FSharp.Control.TaskSeq.Test/TaskSeq.ChunkBySize.Tests.fs
new file mode 100644
index 0000000..fcaf2b7
--- /dev/null
+++ b/src/FSharp.Control.TaskSeq.Test/TaskSeq.ChunkBySize.Tests.fs
@@ -0,0 +1,219 @@
+module TaskSeq.Tests.ChunkBySize
+
+open System
+
+open FsUnitTyped
+open Xunit
+open FsUnit.Xunit
+
+open FSharp.Control
+
+//
+// TaskSeq.chunkBySize
+//
+
+exception SideEffectPastEnd of string
+
+module EmptySeq =
+    [<Theory; ClassData(typeof<TestEmptyVariants>)>]
+    let ``TaskSeq-chunkBySize(0) on empty input should throw InvalidOperation`` variant =
+        fun () ->
+            Gen.getEmptyVariant variant
+            |> TaskSeq.chunkBySize 0
+            |> consumeTaskSeq
+
+        |> should throwAsyncExact typeof<ArgumentException>
+
+    [<Theory; ClassData(typeof<TestEmptyVariants>)>]
+    let ``TaskSeq-chunkBySize(1) has no effect on empty input`` variant =
+        // no `task` block needed
+        Gen.getEmptyVariant variant
+        |> TaskSeq.chunkBySize 1
+        |> verifyEmpty
+
+    [<Theory; ClassData(typeof<TestEmptyVariants>)>]
+    let ``TaskSeq-chunkBySize(99) has no effect on empty input`` variant =
+        // no `task` block needed
+        Gen.getEmptyVariant variant
+        |> TaskSeq.chunkBySize 99
+        |> verifyEmpty
+
+    [<Fact>]
+    let ``TaskSeq-chunkBySize(-1) should throw ArgumentException on any input`` () =
+        fun () ->
+            TaskSeq.empty<int>
+            |> TaskSeq.chunkBySize -1
+            |> consumeTaskSeq
+        |> should throwAsyncExact typeof<ArgumentException>
+
+        fun () ->
+            TaskSeq.init 10 id
+            |> TaskSeq.chunkBySize -1
+            |> consumeTaskSeq
+        |> should throwAsyncExact typeof<ArgumentException>
+
+    [<Fact>]
+    let ``TaskSeq-chunkBySize(-1) should throw ArgumentException before awaiting`` () =
+        fun () ->
+            taskSeq {
+                do! longDelay ()
+
+                if false then
+                    yield 0 // type inference
+            }
+            |> TaskSeq.chunkBySize -1
+            |> ignore // throws even without running the async. Bad coding, don't ignore a task!
+
+        |> should throw typeof<ArgumentException>
+
+module Immutable =
+    [<Theory; ClassData(typeof<TestImmTaskSeq>)>]
+    let ``TaskSeq-chunkBySize returns all items from source in order`` variant = task {
+        do!
+            Gen.getSeqImmutable variant
+            |> TaskSeq.chunkBySize 3
+            |> TaskSeq.collect TaskSeq.ofArray
+            |> verify1To10
+    }
+
+    [<Theory; ClassData(typeof<TestImmTaskSeq>)>]
+    let ``TaskSeq-chunkBySize returns chunks with items in order`` variant = task {
+        do!
+            Gen.getSeqImmutable variant
+            |> TaskSeq.chunkBySize 2
+            |> TaskSeq.toArrayAsync
+            |> Task.map (shouldEqual [| [| 1; 2 |]; [| 3; 4 |]; [| 5; 6 |]; [| 7; 8 |]; [| 9; 10 |] |])
+    }
+
+    [<Theory; ClassData(typeof<TestImmTaskSeq>)>]
+    let ``TaskSeq-chunkBySize returns exactly 'chunkSize' items per chunk`` variant = task {
+        do!
+            Gen.getSeqImmutable variant
+            |> TaskSeq.chunkBySize 1
+            |> TaskSeq.iter (shouldHaveLength 1)
+
+        do!
+            Gen.getSeqImmutable variant
+            |> TaskSeq.chunkBySize 2
+            |> TaskSeq.iter (shouldHaveLength 2)
+
+        do!
+            Gen.getSeqImmutable variant
+            |> TaskSeq.chunkBySize 5
+            |> TaskSeq.iter (shouldHaveLength 5)
+    }
+
+    [<Theory; ClassData(typeof<TestImmTaskSeq>)>]
+    let ``TaskSeq-chunkBySize returns remaining items in last chunk`` variant = task {
+        let verifyChunk chunkSize lastChunkSize =
+            Gen.getSeqImmutable variant
+            |> TaskSeq.chunkBySize chunkSize
+            |> TaskSeq.toArrayAsync
+            |> Task.map (Array.last >> shouldHaveLength lastChunkSize)
+
+        do! verifyChunk 1 1
+        do! verifyChunk 3 1
+        do! verifyChunk 4 2
+        do! verifyChunk 6 4
+        do! verifyChunk 7 3
+        do! verifyChunk 8 2
+        do! verifyChunk 9 1
+    }
+
+    [<Theory; ClassData(typeof<TestImmTaskSeq>)>]
+    let ``TaskSeq-chunkBySize returns all elements when 'chunkSize' > number of items`` variant =
+        Gen.getSeqImmutable variant
+        |> TaskSeq.chunkBySize 11
+        |> TaskSeq.toArrayAsync
+        |> Task.map (Array.exactlyOne >> shouldHaveLength 10)
+
+module SideEffects =
+    [<Theory; ClassData(typeof<TestSideEffectTaskSeq>)>]
+    let ``TaskSeq-chunkBySize gets all items`` variant =
+        Gen.getSeqWithSideEffect variant
+        |> TaskSeq.chunkBySize 5
+        |> TaskSeq.toArrayAsync
+        |> Task.map (shouldEqual [| [| 1..5 |]; [| 6..10 |] |])
+
+    [<Fact>]
+    let ``TaskSeq-chunkBySize prove we execute empty-seq side-effects`` () = task {
+        let mutable i = 0
+
+        let ts = taskSeq {
+            i <- i + 1
+            i <- i + 1
+            i <- i + 1 // we should get here
+        }
+
+        do! ts |> TaskSeq.chunkBySize 1 |> consumeTaskSeq
+        do! ts |> TaskSeq.chunkBySize 2 |> consumeTaskSeq
+        do! ts |> TaskSeq.chunkBySize 3 |> consumeTaskSeq
+        i |> should equal 9
+    }
+
+    [<Fact>]
+    let ``TaskSeq-chunkBySize prove we execute after-effects`` () = task {
+        let mutable i = 0
+
+        let ts = taskSeq {
+            i <- i + 1
+            i <- i + 1
+            yield 42
+            i <- i + 1 // we should get here
+        }
+
+        do! ts |> TaskSeq.chunkBySize 1 |> consumeTaskSeq
+        do! ts |> TaskSeq.chunkBySize 2 |> consumeTaskSeq
+        do! ts |> TaskSeq.chunkBySize 3 |> consumeTaskSeq
+        i |> should equal 9
+    }
+
+    [<Theory; ClassData(typeof<TestSideEffectTaskSeq>)>]
+    let ``TaskSeq-chunkBySize should go over all items`` variant = task {
+        let ts = Gen.getSeqWithSideEffect variant
+        do! ts |> TaskSeq.chunkBySize 1 |> consumeTaskSeq
+        do! ts |> TaskSeq.chunkBySize 2 |> consumeTaskSeq
+        do! ts |> TaskSeq.chunkBySize 3 |> consumeTaskSeq
+        // incl. the iteration of 'last', we reach 40
+        do! ts |> TaskSeq.last |> Task.map (should equal 40)
+    }
+
+    [<Theory; ClassData(typeof<TestSideEffectTaskSeq>)>]
+    let ``TaskSeq-chunkBySize multiple iterations over same sequence`` variant = task {
+        let ts = Gen.getSeqWithSideEffect variant
+        let mutable sum = 0
+
+        do!
+            TaskSeq.chunkBySize 1 ts
+            |> TaskSeq.collect TaskSeq.ofArray
+            |> TaskSeq.iter (fun item -> sum <- sum + item)
+
+        do!
+            TaskSeq.chunkBySize 2 ts
+            |> TaskSeq.collect TaskSeq.ofArray
+            |> TaskSeq.iter (fun item -> sum <- sum + item)
+
+        do!
+            TaskSeq.chunkBySize 3 ts
+            |> TaskSeq.collect TaskSeq.ofArray
+            |> TaskSeq.iter (fun item -> sum <- sum + item)
+
+        do!
+            TaskSeq.chunkBySize 4 ts
+            |> TaskSeq.collect TaskSeq.ofArray
+            |> TaskSeq.iter (fun item -> sum <- sum + item)
+
+        sum |> should equal 820 // side-effected tasks, so 'item' DOES CHANGE, each next iteration starts 10 higher
+    }
+
+    [<Fact>]
+    let ``TaskSeq-chunkBySize prove that an exception from the taskSeq is thrown`` () =
+        let items = taskSeq {
+            yield 42
+            yield! [ 1; 2 ]
+            do SideEffectPastEnd "at the end" |> raise
+            yield 43
+        }
+
+        fun () -> items |> TaskSeq.chunkBySize 2 |> consumeTaskSeq
+        |> should throwAsyncExact typeof<SideEffectPastEnd>
diff --git a/src/FSharp.Control.TaskSeq/TaskSeq.fs b/src/FSharp.Control.TaskSeq/TaskSeq.fs
index 710dadd..a0f59e2 100644
--- a/src/FSharp.Control.TaskSeq/TaskSeq.fs
+++ b/src/FSharp.Control.TaskSeq/TaskSeq.fs
@@ -252,6 +252,8 @@ type TaskSeq private () =
             yield! source2
         }
 
+    static member chunkBySize (chunkSize: int) (source: TaskSeq<'T>) = Internal.chunkBySize chunkSize source
+
     //
     // iter/map/collect functions
     //
diff --git a/src/FSharp.Control.TaskSeq/TaskSeq.fsi b/src/FSharp.Control.TaskSeq/TaskSeq.fsi
index ff98586..3be9662 100644
--- a/src/FSharp.Control.TaskSeq/TaskSeq.fsi
+++ b/src/FSharp.Control.TaskSeq/TaskSeq.fsi
@@ -823,6 +823,15 @@ type TaskSeq =
     /// <exception cref="T:ArgumentNullException">Thrown when the input task sequence is null.</exception>
     static member chooseAsync: chooser: ('T -> #Task<'U option>) -> source: TaskSeq<'T> -> TaskSeq<'U>
 
+    /// <summary>Divides the input sequence into chunks of size at most <c>chunkSize</c>.</summary>
+    ///
+    /// <param name="chunkSize">The maximum size of each chunk.</param>
+    /// <param name="source">The input task sequence.</param>
+    /// <returns>The task sequence divided into chunks.</returns>
+    /// <exception cref="T:System.ArgumentNullException">Thrown when the input task sequence is null.</exception>
+    /// <exception cref="T:System.ArgumentException">Thrown when <c>chunkSize</c> is not positive.</exception>
+    static member chunkBySize: chunkSize: int -> source: TaskSeq<'T> -> TaskSeq<'T[]>
+
     /// <summary>
     /// Returns a new task sequence containing only the elements of the collection
     /// for which the given function <paramref name="predicate" /> returns <see cref="true" />.
diff --git a/src/FSharp.Control.TaskSeq/TaskSeqInternal.fs b/src/FSharp.Control.TaskSeq/TaskSeqInternal.fs
index 66a92f2..9a6e441 100644
--- a/src/FSharp.Control.TaskSeq/TaskSeqInternal.fs
+++ b/src/FSharp.Control.TaskSeq/TaskSeqInternal.fs
@@ -1097,3 +1097,32 @@ module internal TaskSeqInternal =
                     go <- step
 
         }
+
+    let chunkBySize chunkSize (source: TaskSeq<'T>) : TaskSeq<'T[]> =
+        if chunkSize < 1 then
+            invalidArg (nameof chunkSize) $"The value must be positive, but was %i{chunkSize}."
+
+        checkNonNull (nameof source) source
+
+        taskSeq {
+            use e = source.GetAsyncEnumerator CancellationToken.None
+            let mutable go = true
+            let! step = e.MoveNextAsync()
+            go <- step
+
+            if step then
+                let buffer = ResizeArray<_>()
+
+                while go do
+                    buffer.Add e.Current
+
+                    if buffer.Count = chunkSize then
+                        yield buffer.ToArray()
+                        buffer.Clear()
+
+                    let! step = e.MoveNextAsync()
+                    go <- step
+
+                if buffer.Count > 0 then
+                    yield buffer.ToArray()
+        }