Geological Chronicle
Walther is an ancient lunar impact crater in the Moon's southern highland region, spanning 134.23 kilometers in diameter. It joins the crater Deslandres along its western rim, with Aliacensis to the northeast and the irregular crater Nonius connected to its southeastern rim.
The rim of Walther is heavily eroded and incised by lesser impacts, retaining a generally circular form alongside a slight protruding bulge in the western wall. Resurfacing after the original impact left the southwestern half of the floor relatively smooth, while an offset central peak in the northwest quadrant bears wear and several small impact craters.
Seventeenth-century lunar cartographers assigned several competing names to the feature. Michael van Langren's 1645 map designated it Caroli I Reg. Britt. after King Charles I of England, and Johannes Hevelius grouped it with Purbach and Regiomontanus as Mons Libanus. In 1651, Giovanni Riccioli introduced the Latin name Valtherus in honor of German astronomer Bernhard Walther, establishing the nomenclature that became standardized.