diff --git a/doc/site/core/num.markdown b/doc/site/core/num.markdown
index f3c10818..e3d314ed 100644
--- a/doc/site/core/num.markdown
+++ b/doc/site/core/num.markdown
@@ -20,6 +20,11 @@ The arc sine of the number.
 
 The arc tangent of the number.
 
+### **atan**(x)
+
+The arc tangent of the number when divided by `x`, using the signs of the two
+numbers to determine the quadrant of the result.
+
 ### **ceil**
 
 Rounds the number up to the nearest integer.
diff --git a/src/vm/wren_core.c b/src/vm/wren_core.c
index 5ace3893..f3a8687c 100644
--- a/src/vm/wren_core.c
+++ b/src/vm/wren_core.c
@@ -380,7 +380,7 @@ DEF_PRIMITIVE(class_supertype)
 
   // Object has no superclass.
   if (classObj->superclass == NULL) RETURN_NULL;
-  
+
   RETURN_OBJ(classObj->superclass);
 }
 
@@ -924,6 +924,11 @@ DEF_PRIMITIVE(num_atan)
   RETURN_NUM(atan(AS_NUM(args[0])));
 }
 
+DEF_PRIMITIVE(num_atan2)
+{
+  RETURN_NUM(atan2(AS_NUM(args[0]), AS_NUM(args[1])));
+}
+
 DEF_PRIMITIVE(num_ceil)
 {
   RETURN_NUM(ceil(AS_NUM(args[0])));
@@ -1609,6 +1614,7 @@ void wrenInitializeCore(WrenVM* vm)
   PRIMITIVE(vm->numClass, "acos", num_acos);
   PRIMITIVE(vm->numClass, "asin", num_asin);
   PRIMITIVE(vm->numClass, "atan", num_atan);
+  PRIMITIVE(vm->numClass, "atan(_)", num_atan2);
   PRIMITIVE(vm->numClass, "ceil", num_ceil);
   PRIMITIVE(vm->numClass, "cos", num_cos);
   PRIMITIVE(vm->numClass, "floor", num_floor);