diff --git a/src/__tests__/materials.test.ts b/src/__tests__/materials.test.ts
index 383b04e..503ed36 100644
--- a/src/__tests__/materials.test.ts
+++ b/src/__tests__/materials.test.ts
@@ -1,4 +1,5 @@
 import { describe, expect, test } from "bun:test";
+import { MaterialRegistry } from "../materials/registry";
 import {
     BEHAVIOR_GAS,
     BEHAVIOR_LIQUID,
@@ -36,3 +37,38 @@ describe("material types", () => {
         expect(sand.density).toBe(1.5);
     });
 });
+
+describe("MaterialRegistry", () => {
+    test("has air at id 0", () => {
+        const reg = new MaterialRegistry();
+        const air = reg.get(0);
+        expect(air.name).toBe("air");
+        expect(air.density).toBe(0);
+    });
+
+    test("has sand registered", () => {
+        const reg = new MaterialRegistry();
+        const sand = reg.getByName("sand");
+        expect(sand).toBeDefined();
+        expect(sand!.behavior).toBe(BEHAVIOR_POWDER);
+    });
+
+    test("all material ids are unique", () => {
+        const reg = new MaterialRegistry();
+        const ids = reg.all().map((m) => m.id);
+        expect(new Set(ids).size).toBe(ids.length);
+    });
+
+    test("all material ids are in range 0-255", () => {
+        const reg = new MaterialRegistry();
+        for (const m of reg.all()) {
+            expect(m.id).toBeGreaterThanOrEqual(0);
+            expect(m.id).toBeLessThanOrEqual(255);
+        }
+    });
+
+    test("get throws for unknown id", () => {
+        const reg = new MaterialRegistry();
+        expect(() => reg.get(254)).toThrow();
+    });
+});
diff --git a/src/materials/registry.ts b/src/materials/registry.ts
new file mode 100644
index 0000000..4398cd2
--- /dev/null
+++ b/src/materials/registry.ts
@@ -0,0 +1,89 @@
+import {
+    BEHAVIOR_GAS,
+    BEHAVIOR_POWDER,
+    BEHAVIOR_SOLID,
+    type Material,
+} from "./types";
+
+const BUILTIN_MATERIALS: Material[] = [
+    {
+        id: 0,
+        name: "air",
+        behavior: BEHAVIOR_GAS,
+        density: 0,
+        color: [0, 0, 0, 0],
+        hardness: 0,
+        angleOfRepose: 0,
+    },
+    {
+        id: 1,
+        name: "sand",
+        behavior: BEHAVIOR_POWDER,
+        density: 1.5,
+        color: [0.76, 0.7, 0.5, 1.0],
+        hardness: 0.1,
+        angleOfRepose: 34,
+    },
+    {
+        id: 2,
+        name: "dirt",
+        behavior: BEHAVIOR_POWDER,
+        density: 1.3,
+        color: [0.45, 0.32, 0.18, 1.0],
+        hardness: 0.2,
+        angleOfRepose: 40,
+    },
+    {
+        id: 3,
+        name: "rock",
+        behavior: BEHAVIOR_SOLID,
+        density: 2.5,
+        color: [0.5, 0.5, 0.5, 1.0],
+        hardness: 1.0,
+        angleOfRepose: 90,
+    },
+    {
+        id: 4,
+        name: "food",
+        behavior: BEHAVIOR_SOLID,
+        density: 1.0,
+        color: [0.2, 0.8, 0.2, 1.0],
+        hardness: 0.0,
+        angleOfRepose: 0,
+    },
+    {
+        id: 5,
+        name: "home",
+        behavior: BEHAVIOR_SOLID,
+        density: 0,
+        color: [0.3, 0.3, 1.0, 1.0],
+        hardness: 0.0,
+        angleOfRepose: 0,
+    },
+];
+
+export class MaterialRegistry {
+    private byId: Map<number, Material> = new Map();
+    private byName: Map<string, Material> = new Map();
+
+    constructor() {
+        for (const m of BUILTIN_MATERIALS) {
+            this.byId.set(m.id, m);
+            this.byName.set(m.name, m);
+        }
+    }
+
+    get(id: number): Material {
+        const m = this.byId.get(id);
+        if (!m) throw new Error(`Unknown material id: ${id}`);
+        return m;
+    }
+
+    getByName(name: string): Material | undefined {
+        return this.byName.get(name);
+    }
+
+    all(): Material[] {
+        return [...this.byId.values()];
+    }
+}