Apianus is a lunar impact crater that is located on the rugged south-central highlands of the Moon. It is located to the northeast of the crater Aliacensis, and to the northwest of Poisson. The worn crater Krusenstern is attached to the west-northwestern rim.
The outer wall of the crater has been worn and eroded by subsequent impacts, and a pair of small craterlets overlay the rim to the southeast and northeast. The central crater is 63 kilometers in diameter and 2,080 meters deep. The craterlet on the southeast rim, Apianus B, is a member of a cluster of co-joined craterlets that includes Apianus T and Apianus U. The interior floor of the central crater is relatively smooth and lacks a central peak, although the surface appears somewhat convex. Only a few tiny craterlets mark the surface.
A variety of other nearby craters and craterlets belong to Apianus.
The crater is from the Nectarian period, 3.92 to 3.85 billion years ago.
Apianus is named after 16th century German mathematician and astronomer Petrus Apianus. The name applies as official international standard since 1935 and is registered at the International Astronomical Union (IAU).