Keldysh is a lunar impact crater that is located in the northeastern part of the Moon, at the eastern rim of the Mare Frigoris. It lies due north of the prominent crater Atlas, and to the northeast of the notable Hercules.
The crater rim is generally circular, although it gives the appearance of a slight eastward bulge. The rim edge is sharp and displays little appearance of wear, with only a tiny craterlet along the eastern edge. The inner wall slopes down without terraces to the ejecta along the base. The interior floor is relatively featureless and is free of notable impacts or ridges.
This crater was previously designated Hercules A, a satellite crater of Hercules, before being renamed by the IAU.
Keldysh can refer to one of the following.
Leonid Keldysh (b. 1931), a Russian physicist, former director of the Lebedev Physical Institute (1988-1994), now physics faculty at Texas A&M University
- Keldysh formalism for studying non-equilibrium quantum systems
Mstislav Keldysh (1911-1978), a Russian mathematician, president of the Soviet Academy of Sciences (1961-1978)
- Akademik Mstislav Keldysh, a Russian scientific research vessel named after him and renowned for its visits to the wreck of the RMS Titanic
- Keldysh Institute of Applied Mathematics, a Russian research institute named after him
- Keldysh (crater), a crater on the Moon named after him
- 2186 Keldysh, an asteroid named after him
- Lyudmila Keldysh (1904–1976), mathematician, sister of Mstislav, wife of Pyotr Novikov
(1907–1995), a Russian musician