Who was the first American to ride to space on board a Russian vehicle?

Norman Earl Thagard (born July 3, 1943), (Capt, USMC, Ret.), is an American scientist and former U.S. Marine Corps officer and naval aviator and NASA astronaut. He is the first American to ride to space on board a Russian vehicle, and can be considered the first American cosmonaut. He did on this on March 14, 1995, in the Soyuz TM-21 spacecraft for the Russian Mir-18 mission.

Thagard was selected as an astronaut candidate by NASA in January 1978. In August 1979, he completed a one-year training and evaluation period, making him eligible for assignment as a Mission Specialist on future Space Shuttle flights. A veteran of five space flights, he logged over 140 days in space. He was a Mission Specialist on STS-7 in 1983, STS-51-B in 1985, STS-30 in 1989, was the Payload Commander on STS-42 in 1992, and was the cosmonaut/researcher on the Russian Mir-18 mission in 1995.