Keldysh (Russian: ) may refer to:
Science Keldysh formalism, for studying non-equilibrium quantum systems Akademik Mstislav Keldysh, a 1980 Russian scientific research vessel renowned for its visits to the wreck of the RMS Titanic Keldysh Institute of Applied Mathematics, a Russian research institute Keldysh (crater), a crater on the Moon 2186 Keldysh, an asteroid
People Leonid Keldysh (1931–2016), Russian physicist, former director of the Lebedev Physical Institute (1988–1994), later a member of the physics faculty at Texas A&M University Mstislav Keldysh (1911–1978), Russian mathematician, president of the Soviet Academy of Sciences (1961–1978) Lyudmila Keldysh (1904–1976), mathematician, sister of Mstislav, wife of Pyotr Novikov