diff --git a/Cargo.toml b/Cargo.toml
index 43a3a87..956421f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -101,6 +101,7 @@ rand-builtins = ["rng"]
 yaml-builtins = ["dep:serde_yaml"]
 urlquery-builtins = ["dep:form_urlencoded", "dep:urlencoding"]
 time-builtins = ["time", "dep:chrono-tz", "dep:duration-str", "dep:chronoutil"]
+object-builtins = []
 
 all-crypto-builtins = [
   "crypto-digest-builtins",
@@ -122,6 +123,7 @@ all-builtins = [
   "yaml-builtins",
   "urlquery-builtins",
   "time-builtins",
+  "object-builtins",
 ]
 
 [[test]]
diff --git a/src/builtins/impls/mod.rs b/src/builtins/impls/mod.rs
index 8013b1a..d49f63f 100644
--- a/src/builtins/impls/mod.rs
+++ b/src/builtins/impls/mod.rs
@@ -32,6 +32,7 @@ pub mod io;
 #[cfg(feature = "json-builtins")]
 pub mod json;
 pub mod net;
+#[cfg(feature = "object-builtins")]
 pub mod object;
 pub mod opa;
 #[cfg(feature = "rng")]
diff --git a/src/builtins/impls/object.rs b/src/builtins/impls/object.rs
index 82cdf65..4cc0a76 100644
--- a/src/builtins/impls/object.rs
+++ b/src/builtins/impls/object.rs
@@ -14,12 +14,40 @@
 
 //! Builtins to help handling JSON objects
 
-use anyhow::{bail, Result};
+use anyhow::Result;
+use serde_json::Value;
 
 /// Creates a new object that is the asymmetric union of all objects merged from
 /// left to right. For example: `object.union_n([{"a": 1}, {"b": 2}, {"a": 3}])`
 /// will result in `{"b": 2, "a": 3}`.
 #[tracing::instrument(name = "object.union_n", err)]
-pub fn union_n(objects: Vec<serde_json::Value>) -> Result<serde_json::Value> {
-    bail!("not implemented");
+pub fn union_n(objects: Vec<Value>) -> Result<Value> {
+    let mut result = serde_json::Value::Object(serde_json::Map::default());
+    for object in objects {
+        merge_value(&mut result, &object);
+    }
+
+    Ok(result)
+}
+
+fn merge_value(a: &mut Value, b: &Value) {
+    match (a, b) {
+        (Value::Object(ref mut a), &Value::Object(ref b)) => {
+            for (k, v) in b {
+                merge_value(a.entry(k).or_insert(Value::Null), v);
+            }
+        }
+        (Value::Array(ref mut a), &Value::Array(ref b)) => {
+            *a = vec![];
+            a.extend(b.clone());
+        }
+        (Value::Array(ref mut a), &Value::Object(ref b)) => {
+            *a = vec![];
+            a.extend([Value::Object(b.clone())]);
+        }
+        (_, Value::Null) => {}
+        (a, b) => {
+            *a = b.clone();
+        }
+    }
 }
diff --git a/src/builtins/mod.rs b/src/builtins/mod.rs
index 392f7f6..c5c20ca 100644
--- a/src/builtins/mod.rs
+++ b/src/builtins/mod.rs
@@ -106,7 +106,10 @@ pub fn resolve<C: EvaluationContext>(name: &str) -> Result<Box<dyn Builtin<C>>>
         "net.cidr_expand" => Ok(self::impls::net::cidr_expand.wrap()),
         "net.cidr_merge" => Ok(self::impls::net::cidr_merge.wrap()),
         "net.lookup_ip_addr" => Ok(self::impls::net::lookup_ip_addr.wrap()),
+
+        #[cfg(feature = "object-builtins")]
         "object.union_n" => Ok(self::impls::object::union_n.wrap()),
+
         "opa.runtime" => Ok(self::impls::opa::runtime.wrap()),
 
         #[cfg(feature = "rng")]
diff --git a/tests/infra-fixtures/test-object.rego b/tests/infra-fixtures/test-object.rego
new file mode 100644
index 0000000..75249e8
--- /dev/null
+++ b/tests/infra-fixtures/test-object.rego
@@ -0,0 +1,9 @@
+package test
+
+object_1 := object.union_n([{"a": 1}, {"b": 2}, {"a": 3}])
+
+object_2 := object.union_n([{"a": 1}, {"b": 2}, {"a": 3, "b": 1}])
+
+object_override_by_string := object.union_n([{"a": 1}, {"b": 2}, {"a": "3"}])
+
+recursive := object.union_n([{"a": {"b": [1], "c": 1}}, {"a": {"b": [1, 2, 3]}}])
diff --git a/tests/smoke_test.rs b/tests/smoke_test.rs
index cf70c51..3efade7 100644
--- a/tests/smoke_test.rs
+++ b/tests/smoke_test.rs
@@ -121,6 +121,7 @@ integration_test!(test_rand, "test-rand");
 integration_test!(test_yaml, "test-yaml");
 integration_test!(test_urlquery, "test-urlquery");
 integration_test!(test_time, "test-time");
+integration_test!(test_object, "test-object");
 
 /*
 #[tokio::test]
diff --git a/tests/snapshots/smoke_test__object.snap b/tests/snapshots/smoke_test__object.snap
new file mode 100644
index 0000000..0b99046
--- /dev/null
+++ b/tests/snapshots/smoke_test__object.snap
@@ -0,0 +1,21 @@
+---
+source: tests/smoke_test.rs
+expression: "test_policy(\"test-object\", None).await.expect(\"error in test suite\")"
+---
+- result:
+    object_1:
+      a: 3
+      b: 2
+    object_2:
+      a: 3
+      b: 1
+    object_override_by_string:
+      a: "3"
+      b: 2
+    recursive:
+      a:
+        b:
+          - 1
+          - 2
+          - 3
+        c: 1
\ No newline at end of file