Planck is a large lunar impact crater, approximately 319 kilometers in diameter, that is located in the southern hemisphere of the Moon, on the far side as seen from the Earth.

[2] According to a 2012 study, Planck formed roughly 4.09 Ga (billion years) ago, partially resurfacing the area of the South Pole-Aitken basin that it impacted.

[2] Like many lunar formations of this size, the outer rim has been damaged and eroded by lesser impacts, leaving a rugged ring of peaks and ridges that is notched and incised by small craters.

The western rim of this walled plain is neatly overlain by a long lunar valley designated the Vallis Planck.

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