diff --git a/lib/ocaml/runtime.sx b/lib/ocaml/runtime.sx
index ce31974f..5afd020f 100644
--- a/lib/ocaml/runtime.sx
+++ b/lib/ocaml/runtime.sx
@@ -389,6 +389,90 @@
        | Some v -> v
      let mem t k = _hashtbl_mem t k
      let length t = _hashtbl_length t
+   end ;;
+
+   module Map = struct
+     module Make (Ord) = struct
+       let empty = []
+
+       let rec add k v m =
+         match m with
+         | [] -> [(k, v)]
+         | (k2, v2) :: rest ->
+           begin
+             let c = Ord.compare k k2 in
+             if c = 0 then (k, v) :: rest
+             else if c < 0 then (k, v) :: m
+             else (k2, v2) :: add k v rest
+           end
+
+       let rec find_opt k m =
+         match m with
+         | [] -> None
+         | (k2, v) :: rest ->
+           if Ord.compare k k2 = 0 then Some v
+           else find_opt k rest
+
+       let find k m =
+         match find_opt k m with
+         | None -> failwith \"Map.find: not found\"
+         | Some v -> v
+
+       let rec mem k m =
+         match m with
+         | [] -> false
+         | (k2, _) :: rest -> if Ord.compare k k2 = 0 then true else mem k rest
+
+       let rec remove k m =
+         match m with
+         | [] -> []
+         | (k2, v) :: rest ->
+           if Ord.compare k k2 = 0 then rest else (k2, v) :: remove k rest
+
+       let rec bindings m = m
+
+       let rec cardinal m =
+         match m with
+         | [] -> 0
+         | _ :: t -> 1 + cardinal t
+     end
+   end ;;
+
+   module Set = struct
+     module Make (Ord) = struct
+       let empty = []
+
+       let rec mem x s =
+         match s with
+         | [] -> false
+         | h :: t ->
+           let c = Ord.compare x h in
+           if c = 0 then true
+           else if c < 0 then false
+           else mem x t
+
+       let rec add x s =
+         match s with
+         | [] -> [x]
+         | h :: t ->
+           let c = Ord.compare x h in
+           if c = 0 then s
+           else if c < 0 then x :: s
+           else h :: add x t
+
+       let rec remove x s =
+         match s with
+         | [] -> []
+         | h :: t ->
+           if Ord.compare x h = 0 then t else h :: remove x t
+
+       let rec elements s = s
+
+       let rec cardinal s =
+         match s with
+         | [] -> 0
+         | _ :: t -> 1 + cardinal t
+     end
    end")
 
 (define ocaml-stdlib-loaded false)
diff --git a/lib/ocaml/test.sh b/lib/ocaml/test.sh
index a9eec931..0c2fdd5d 100755
--- a/lib/ocaml/test.sh
+++ b/lib/ocaml/test.sh
@@ -1024,6 +1024,16 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 3204)
 (eval "(ocaml-run \"Sys.executable_name\")")
 
+;; ── Map.Make / Set.Make functors ──────────────────────────────
+(epoch 3300)
+(eval "(ocaml-run-program \"module IntOrd = struct let compare a b = compare a b end ;; module IntMap = Map.Make(IntOrd) ;; let m = IntMap.add 1 \\\"a\\\" IntMap.empty ;; let m = IntMap.add 2 \\\"b\\\" m ;; IntMap.find 1 m\")")
+(epoch 3301)
+(eval "(ocaml-run-program \"module IntOrd = struct let compare a b = compare a b end ;; module IntMap = Map.Make(IntOrd) ;; IntMap.cardinal (IntMap.add 1 \\\"a\\\" (IntMap.add 2 \\\"b\\\" IntMap.empty))\")")
+(epoch 3302)
+(eval "(ocaml-run-program \"module IntOrd = struct let compare a b = compare a b end ;; module IntSet = Set.Make(IntOrd) ;; IntSet.elements (IntSet.add 3 (IntSet.add 1 (IntSet.add 2 IntSet.empty)))\")")
+(epoch 3303)
+(eval "(ocaml-run-program \"module IntOrd = struct let compare a b = compare a b end ;; module IntSet = Set.Make(IntOrd) ;; IntSet.mem 2 (IntSet.add 3 (IntSet.add 1 (IntSet.add 2 IntSet.empty)))\")")
+
 EPOCHS
 
 OUTPUT=$(timeout 180 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -1620,6 +1630,12 @@ check 3202 "Sys.unix"                     'true'
 check 3203 "Sys.win32"                    'false'
 check 3204 "Sys.executable_name"          '"ocaml-on-sx"'
 
+# ── Map.Make / Set.Make ────────────────────────────────────────
+check 3300 "Map.find via functor"         '"a"'
+check 3301 "Map.cardinal"                 '2'
+check 3302 "Set.elements sorted"          '(1 2 3)'
+check 3303 "Set.mem"                      'true'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "ok $PASS/$TOTAL OCaml-on-SX tests passed"
diff --git a/plans/ocaml-on-sx.md b/plans/ocaml-on-sx.md
index bdec70c7..d009b9d7 100644
--- a/plans/ocaml-on-sx.md
+++ b/plans/ocaml-on-sx.md
@@ -286,8 +286,11 @@ SX CEK evaluator (both JS and OCaml hosts)
 - [ ] `Int`/`Float`: arithmetic, `to_string`, `of_string_opt`, `min_int`, `max_int`.
 - [ ] `Hashtbl`: `create`, `add`, `replace`, `find`, `find_opt`, `remove`, `mem`,
       `iter`, `fold`, `length` — backed by SX mutable dict.
-- [ ] `Map.Make` functor — balanced BST backed by SX sorted dict.
-- [ ] `Set.Make` functor.
+- [x] `Map.Make` functor — sorted association list backed
+      (insert/find/remove/mem/cardinal/bindings); not a balanced tree
+      but linear with parametric `Ord` ordering.
+- [x] `Set.Make` functor — sorted list backed
+      (add/mem/remove/elements/cardinal).
 - [ ] `Printf`: `sprintf`, `printf`, `eprintf` — format strings via `(format ...)`.
 - [ ] `Sys`: `argv`, `getenv_opt`, `getcwd` — via `perform` IO.
 - [ ] Scoreboard runner: `lib/ocaml/conformance.sh` + `scoreboard.json`.
@@ -383,6 +386,14 @@ the "mother tongue" closure: OCaml → SX → OCaml. This means:
 
 _Newest first._
 
+- 2026-05-08 Phase 6 — `Map.Make` / `Set.Make` functors written in
+  OCaml (+4 tests, 418 total). Sorted association list / sorted list
+  backed (linear ops, but correct). Both take an `Ord` module supplying
+  `compare`. Tested: `module IntMap = Map.Make(IntOrd) ;; IntMap.find
+  …` and `IntSet.elements (IntSet.add 3 (IntSet.add 1 …))` returning
+  `[1; 2; 3]`. Strong substrate-validation for the functor system —
+  Map.Make is a non-trivial functor implemented entirely on top of the
+  OCaml-on-SX evaluator.
 - 2026-05-08 Phase 6 — `Sys` module constants (+5 tests, 414 total).
   os_type, word_size, max_array_length, max_string_length,
   executable_name, big_endian, unix, win32, cygwin. Constants-only