Mons Rümker is an isolated volcanic formation that is located in the northwest part of the Moon's near side, at selenographic coordinates 40.8° N, 58.1° W. The feature forms a large, elevated mound in the northern part of the Oceanus Procellarum lunar mare. The mound has a diameter of 70 km, and climbs to a maximum elevation of about 500 m. It was named for Karl L. C. Rümker .

The Mons Rümker has a concentration of lunar domes—rounded bulges across the top, some of which contain a small craterlet at the peak. These are wide, circular features with a gentle slope rising in elevation a few hundred meters to the mid-point. Lunar domes are the result of lava erupting from localized vents followed by relatively slow cooling.