diff --git a/.github/workflows/benchmark.yml b/.github/workflows/benchmark.yml
new file mode 100644
index 0000000..b35da5d
--- /dev/null
+++ b/.github/workflows/benchmark.yml
@@ -0,0 +1,29 @@
+name: Benchmark this PR
+
+on:
+  pull_request:
+    branches: [master]
+    paths-ignore: ['docs/**']
+
+permissions:
+  pull-requests: write
+  contents: read
+
+jobs:
+  benchmark:
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    strategy:
+      fail-fast: false
+      matrix:
+        version: ["1", "lts"]
+    env:
+      # Force consistent Julia depot path for self-hosted runners
+      JULIA_DEPOT_PATH: ~/.julia
+    steps:
+      - uses: MilesCranmer/AirspeedVelocity.jl@action-v1
+        with:
+          julia-version: ${{ matrix.version }}
+          script: "benchmark/benchmarks.jl"
+          extra-pkgs: "StableRNGs"
+          job-summary: true
diff --git a/benchmark/benchmarks.jl b/benchmark/benchmarks.jl
new file mode 100644
index 0000000..b988ba3
--- /dev/null
+++ b/benchmark/benchmarks.jl
@@ -0,0 +1,71 @@
+using MultiScaleArrays, BenchmarkTools
+using StableRNGs
+
+const SUITE = BenchmarkGroup()
+const rng = StableRNG(123)
+
+# Minimal multi-scale hierarchy: Cell -> Population -> Tissue
+struct Cell{B} <: AbstractMultiScaleArrayLeaf{B}
+    values::Vector{B}
+end
+struct Population{T <: AbstractMultiScaleArray, B <: Number} <:
+    AbstractMultiScaleArray{B}
+    nodes::Vector{T}
+    values::Vector{B}
+    end_idxs::Vector{Int}
+end
+struct Tissue{T <: AbstractMultiScaleArray, B <: Number} <:
+    AbstractMultiScaleArrayHead{B}
+    nodes::Vector{T}
+    values::Vector{B}
+    end_idxs::Vector{Int}
+end
+
+function make_tissue(npops, ncells)
+    cells = [Cell(rand(rng, 4)) for _ in 1:ncells]
+    pops = [construct(Population, deepcopy(cells)) for _ in 1:npops]
+    return construct(Tissue, pops)
+end
+
+tissue = make_tissue(10, 20)
+tissue_big = make_tissue(50, 40)
+
+# =============================================================================
+# Construction
+# =============================================================================
+
+SUITE["construct"] = BenchmarkGroup()
+
+cells_small = [Cell(rand(rng, 4)) for _ in 1:20]
+pops_small = [construct(Population, deepcopy(cells_small)) for _ in 1:10]
+
+SUITE["construct"]["population"] = @benchmarkable construct(
+    Population, $(deepcopy(cells_small))
+)
+SUITE["construct"]["tissue"] = @benchmarkable construct(
+    Tissue, $(deepcopy(pops_small))
+)
+
+# =============================================================================
+# Traversal
+# =============================================================================
+
+SUITE["iterate"] = BenchmarkGroup()
+
+SUITE["iterate"]["level_iter"] = @benchmarkable collect(level_iter($tissue, 1))
+SUITE["iterate"]["level_iter_big"] = @benchmarkable collect(
+    level_iter($tissue_big, 2)
+)
+SUITE["iterate"]["eachindex"] = @benchmarkable sum(x -> x, $tissue_big)
+
+# =============================================================================
+# Node mutation
+# =============================================================================
+
+SUITE["nodes"] = BenchmarkGroup()
+
+SUITE["nodes"]["add_node!"] = @benchmarkable add_node!(t, p) setup = (
+    t = make_tissue(10, 20);
+    p = construct(Population, [Cell(rand($rng, 4)) for _ in 1:5])
+)
+SUITE["nodes"]["num_nodes"] = @benchmarkable num_nodes($tissue_big)