diff --git a/lib/ocaml/baseline/dijkstra.ml b/lib/ocaml/baseline/dijkstra.ml
new file mode 100644
index 00000000..39d36f7b
--- /dev/null
+++ b/lib/ocaml/baseline/dijkstra.ml
@@ -0,0 +1,37 @@
+let n = 5
+
+let edges = [|
+  [(1, 4); (2, 1)];
+  [(3, 1)];
+  [(1, 2); (3, 5)];
+  [(4, 3)];
+  []
+|]
+
+let dijkstra src =
+  let dist = Array.make n 1000000 in
+  dist.(src) <- 0;
+  let visited = Array.make n false in
+  for _ = 0 to n - 1 do
+    let u = ref (-1) in
+    let best = ref 1000000 in
+    for v = 0 to n - 1 do
+      if (not visited.(v)) && dist.(v) < !best then begin
+        best := dist.(v);
+        u := v
+      end
+    done;
+    if !u >= 0 then begin
+      visited.(!u) <- true;
+      List.iter (fun (v, w) ->
+        if dist.(!u) + w < dist.(v) then
+          dist.(v) <- dist.(!u) + w
+      ) edges.(!u)
+    end
+  done;
+  dist
+
+;;
+
+let d = dijkstra 0 in
+d.(4)
diff --git a/lib/ocaml/baseline/expected.json b/lib/ocaml/baseline/expected.json
index ec5db123..2c9d525b 100644
--- a/lib/ocaml/baseline/expected.json
+++ b/lib/ocaml/baseline/expected.json
@@ -25,6 +25,7 @@
   "coin_change.ml": 6,
   "count_change.ml": 406,
   "csv.ml": 10,
+  "dijkstra.ml": 7,
   "exception_handle.ml": 4,
   "exception_user.ml": 26,
   "euler1.ml": 233168,
diff --git a/plans/ocaml-on-sx.md b/plans/ocaml-on-sx.md
index 3094e11d..6d09d730 100644
--- a/plans/ocaml-on-sx.md
+++ b/plans/ocaml-on-sx.md
@@ -407,6 +407,15 @@ _Newest first._
   binary search tree (`type 'a tree = Leaf | Node of 'a * 'a tree *
   'a tree`) with insert + in-order traversal. Tests parametric ADT,
   recursive match, List.append, List.fold_left.
+- 2026-05-10 Phase 5.1 — dijkstra.ml baseline (single-source shortest
+  path on a 5-node weighted graph, dist 0→4 = 7). O(n²) array-based
+  Dijkstra: at each step, scan unvisited vertices for the minimum
+  tentative distance, relax outgoing edges. Adjacency stored as
+  `(int * int) list array` literal with int-pair tuples for
+  destination + weight. The optimal path 0→2→1→3→4 has weight
+  1+2+1+3=7. Tests array of lists of pairs, List.iter with
+  destructuring closure, in-place dist mutation. 141 baseline
+  programs total.
 - 2026-05-10 Phase 5.1 — kmp.ml baseline (KMP string search, count
   occurrences of "abab" in "abababcabababcababcc" = 5). Two-phase
   classic: build failure table in O(m), then linear scan in O(n).