diff --git a/modules/arena.kl b/modules/arena.kl
new file mode 100644
index 0000000..001fcb1
--- /dev/null
+++ b/modules/arena.kl
@@ -0,0 +1,45 @@
+OS   :: #import "os_windows.kl"
+Base :: #import "base.kl"
+ArenaDI: U64
+
+ADDITIONAL_COMMIT_SIZE :: 1024*1024
+DEFAULT_RESERVE_SIZE   :: 1024*1024*1024
+DEFAULT_ALIGNMENT      :: 8
+
+Arena :: struct
+  di: U64 // @debug_id
+  memory: OS.Memory
+  alignment: U64
+  len: U64
+
+Init :: (a: *Arena)
+  a.memory    = OS.Reserve(DEFAULT_RESERVE_SIZE)
+  a.alignment = DEFAULT_ALIGNMENT
+  a.di        = ArenaDI++
+  // a.allocator.proc = arena_allocator_proc
+
+PushSize :: (a: *Arena, size: Base.SizeU): *void
+  generous_size := size + a.alignment
+  if a.len + generous_size > a.memory.commit
+    if a.memory.reserve == 0
+      Init(a)
+    result := OS.Commit(&a.memory, generous_size + ADDITIONAL_COMMIT_SIZE)
+    Assert(result == true)
+  a.len = Base.AlignUp(a.len, a.alignment)
+  Assert(a.memory.reserve  > a.len + a.memory.commit)
+  result: *void = a.memory.data + a.len
+  a.len += size
+  return result
+
+// @todo: Make this compile time thing!!!
+// This probably will wait till polymorphism stuff
+// something like this:
+// PushType :: (a: *Arena, type: $T): *T
+//
+PushType :: (a: *Arena, type: Type): *void
+  type_info := get_type_info(type)
+  Assert(type_info != 0)
+  return PushSize(a, type_info.size->Base.SizeU)
+
+Release :: (a: *Arena)
+  OS.Release(&a.memory)