Harpalus is a young lunar impact crater that lies on the Mare Frigoris, at the eastern edge of the Sinus Roris.

It is surrounded by an outer rampart of ejecta, most notably towards the north, and is at the center of a small ray system.

It was chosen by artist Chesley Bonestell as it had a relatively high latitude and the Earth could be realistically displayed at a low altitude during camera shots.

However, the resulting clay model depicted crazing (net-like cracks) across the crater floor, an addition to which Bonestell objected.

By convention, these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Harpalus.