Theophilus est un cratère de 100 Km et profond de 4400 m qui se trouve entre le Golfe des Aspérités (Sinus Asperitatis) dans le nord et la Mer du Nectar (Mare Nectaris) au sud-est. Il s'impose partiellement sur le cratère Cyrillus (98 Km) au sud-ouest. À l'est, on trouve le cratère Mädle (28 Km, 2670 m)  et  a  l'ouest, en forme de promontoire, Mons Penck (30 Km, 4000 m). La muraille de Theophilus a une surface  intérieure large, en terrasse

qui montre des éboulements. L'extérieur a un rempart large et torturé. Sur le mur Nord-ouest repose Theophilus B (8 Km). Le plancher du cratère est relativement plat avec une quadruple crête centrale qui s'élève à une hauteur d'environ 2 kilomètres. Les pentes Ouest de ces pics sont plus larges et plus irrégulières, tandis que les crêtes descendent plus brusquement sur les cotés nordiques et occidentaux.

 (English version, Wikipedia copyright)

Theophilus is a prominent lunar impact crater that lies between Sinus Asperitatis in the north and Mare Nectaris to the southeast. It partially intrudes into the comparably-sized Cyrillus crater to the southwest. To the east is the smaller Mädler crater and further to the south-southeast is Beaumont crater. To the west-northwest is Mons Penck, a peak forming a promontory arm on the Rupes Altai.
The Rev. T. W. Webb described this as "the deepest of all visible craters". The rim of Theophilus crater has a wide, terraced inner surface that shows indications of landslips. The exterior has a wide, wrinkled rampart that descends about 1.4 kilometers to the surrounding maria. The largest impact crater of signifance on the wall is the small Theophilus B on the inside of the northwest rim. Most of the rays from this crater has been weathered away, although a few are still visible.
The floor of the crater is relatively flat, and it has a large, triple-peaked central crater that climbs to a height of about 2 kilometers above the floor. The western peak is designated Psi (ψ), the eastern Phi (φ), and the northern peak is Alpha (α) Theophilus. The western slopes of this ridge are wider and more irregular, whereas the peaks descend more sharply to the floor on the northern and western faces.
The Apollo 16 mission collected several pieces of basalt that are believed to be ejecta from the formation of the Theophilus crater.