Kao is a small lunar impact crater that is located near the eastern limb of the Moon.

This crater forms part of a merged pair with Helmert to the south.

There is a gap in the sides of the crater where they are joined together, and they share a common floor that has been resurfaced by lava.

The outer rim of this crater now forms little more than a shallow ring in the surface, with the rim lowest along the northern side.

However, there is a small crater along the southeastern edge where the rim joins that of Helmert.