diff --git a/src/builtin/range.zig b/src/builtin/range.zig
index a934bb6d..ba168637 100644
--- a/src/builtin/range.zig
+++ b/src/builtin/range.zig
@@ -111,3 +111,29 @@ pub fn intersect(ctx: *obj.NativeCtx) c_int {
 
     return 1;
 }
+
+pub fn @"union"(ctx: *obj.NativeCtx) c_int {
+    const rangeA = ctx.vm.peek(1).obj().access(obj.ObjRange, .Range, ctx.vm.gc).?;
+    const rangeB = ctx.vm.peek(0).obj().access(obj.ObjRange, .Range, ctx.vm.gc).?;
+
+    ctx.vm.push(
+        Value.fromObj((ctx.vm.gc.allocateObject(
+            obj.ObjRange,
+            obj.ObjRange{
+                .high = @min(
+                    @min(rangeB.low, rangeB.high),
+                    @min(rangeA.low, rangeA.high),
+                ),
+                .low = @max(
+                    @max(rangeB.low, rangeB.high),
+                    @max(rangeA.low, rangeA.high),
+                ),
+            },
+        ) catch {
+            ctx.vm.panic("Out of memory");
+            unreachable;
+        }).toObj()),
+    );
+
+    return 1;
+}
diff --git a/src/obj.zig b/src/obj.zig
index 6ce4695b..839e4353 100644
--- a/src/obj.zig
+++ b/src/obj.zig
@@ -2501,6 +2501,7 @@ pub const ObjRange = struct {
             .{ "invert", buzz_builtin.range.invert },
             .{ "subsetOf", buzz_builtin.range.subsetOf },
             .{ "intersect", buzz_builtin.range.intersect },
+            .{ "union", buzz_builtin.range.@"union" },
         },
     );
 
@@ -2511,6 +2512,7 @@ pub const ObjRange = struct {
             .{ "invert", "extern Function invert() > rg" },
             .{ "subsetOf", "extern Function subsetOf(rg other) > bool" },
             .{ "intersect", "extern Function intersect(rg other) > rg" },
+            .{ "union", "extern Function union(rg other) > rg" },
         },
     );