diff --git a/builtins/array.c b/builtins/array.c
index a6e0dca..abc9f92 100644
--- a/builtins/array.c
+++ b/builtins/array.c
@@ -634,4 +634,22 @@ public void Array$heapify(array_t *heap, closure_t comparison, int64_t padded_it
     ARRAY_DECREF(*heap);
 }
 
+public Int_t Array$binary_search(array_t array, void *target, closure_t comparison)
+{
+    typedef int32_t (*cmp_fn_t)(void*, void*, void*);
+    int64_t lo = 0, hi = array.length-1;
+    while (lo <= hi) {
+        int64_t mid = (lo + hi) / 2;
+        int32_t cmp = ((cmp_fn_t)comparison.fn)(
+            array.data + array.stride*mid, target, comparison.userdata);
+        if (cmp == 0)
+            return I(mid+1);
+        else if (cmp < 0)
+            lo = mid + 1;
+        else if (cmp > 0)
+            hi = mid - 1;
+    }
+    return I(lo+1); // Return the index where the target would be inserted
+}
+
 // vim: ts=4 sw=0 et cino=L2,l1,(0,W4,m1,\:0
diff --git a/builtins/array.h b/builtins/array.h
index a3305ca..88184f8 100644
--- a/builtins/array.h
+++ b/builtins/array.h
@@ -85,5 +85,8 @@ void Array$heap_pop(array_t *heap, closure_t comparison, int64_t padded_item_siz
 #define Array$heap_pop_value(heap, comparison, padded_item_size, type) \
     ({ array_t *_heap = heap; if (_heap->length == 0) fail("Attempt to pop from an empty array"); \
      type value = *(type*)_heap->data; Array$heap_pop(_heap, comparison, padded_item_size); value; })
+Int_t Array$binary_search(array_t array, void *target, closure_t comparison);
+#define Array$binary_search_value(array, target, comparison) \
+    ({ __typeof(target) _target = target; Array$binary_search(array, &_target, comparison); })
 
 // vim: ts=4 sw=0 et cino=L2,l1,(0,W4,m1,\:0
diff --git a/compile.c b/compile.c
index 516ca36..f7589ea 100644
--- a/compile.c
+++ b/compile.c
@@ -2166,6 +2166,15 @@ CORD compile(env_t *env, ast_t *ast)
                 arg_t *arg_spec = new(arg_t, .name="by", .type=Type(ClosureType, .fn=fn_t), .default_val=default_cmp);
                 CORD arg_code = compile_arguments(env, ast, arg_spec, call->args);
                 return CORD_all("Array$heap_pop_value(", self, ", ", arg_code, ", ", padded_item_size, ", ", compile_type(item_t), ")");
+            } else if (streq(call->name, "binary_search")) {
+                CORD self = compile_to_pointer_depth(env, call->self, 0, false);
+                type_t *item_ptr = Type(PointerType, .pointed=item_t, .is_stack=true);
+                type_t *fn_t = Type(FunctionType, .args=new(arg_t, .name="x", .type=item_ptr, .next=new(arg_t, .name="y", .type=item_ptr)),
+                                    .ret=Type(IntType, .bits=32));
+                ast_t *default_cmp = FakeAST(InlineCCode, .code=CORD_all("((closure_t){.fn=generic_compare, .userdata=(void*)", compile_type_info(env, item_t), "})"), .type=NewTypeAST(NULL, NULL, NULL, FunctionTypeAST));
+                arg_t *arg_spec = new(arg_t, .name="target", .type=item_t, .next=new(arg_t, .name="by", .type=Type(ClosureType, .fn=fn_t), .default_val=default_cmp));
+                CORD arg_code = compile_arguments(env, ast, arg_spec, call->args);
+                return CORD_all("Array$binary_search_value(", self, ", ", arg_code, ")");
             } else if (streq(call->name, "clear")) {
                 CORD self = compile_to_pointer_depth(env, call->self, 1, false);
                 (void)compile_arguments(env, ast, NULL, call->args);
diff --git a/typecheck.c b/typecheck.c
index 1100aed..2814bd0 100644
--- a/typecheck.c
+++ b/typecheck.c
@@ -728,6 +728,7 @@ type_t *get_type(env_t *env, ast_t *ast)
             else if (streq(call->name, "heapify")) return Type(VoidType);
             else if (streq(call->name, "heap_push")) return Type(VoidType);
             else if (streq(call->name, "heap_pop")) return Match(self_value_t, ArrayType)->item_type;
+            else if (streq(call->name, "binary_search")) return INT_TYPE;
             else code_err(ast, "There is no '%s' method for arrays", call->name);
         }
         case SetType: {