Russia's Valeri Polyakov holds the record for the ''Longest Single Mission Stay in Space '' - 438 Days

Longest single trip to space - 437.7 days, Valeri Polyakov, Russia. Jan. 1, 1994 to March 22, 1995, to the Russian space station Mir

 

Longest cumulative time in space - 803.4 days, Sergei Krikalev, Russia (six spaceflights)

US Astronaut Jeff Williams(58)Sets US Space Record

US Astronaut Jeff Williams, International Space Station (ISS) Expedition 48 commander, recently surpassed former astronaut Scott Kelly for the all-time U.S. endurance record in space – more than 520 days as of  Wednesday Aug. 24,2016

By the time he returns home on Sept. 6, he will have accumulated more than 534 days above Earth over four missions.


US Astronaut Jeff  Williams surpassed Kelly, who himself took the record from Mike Fincke back in Oct 2015