John Herschel Glenn Jr. (born July 18, 1921, in Cambridge, Ohio) is a former astronaut and U.S. politician who became the first American to orbit the Earth, and later, United States Senator. Glenn began his career as a Marine Corps fighter pilot before joining NASA's Mercury program, NASA's original astronaut group. He orbited the Earth aboard Friendship 7 in 1962. After retiring from NASA, he ran as a Democrat and represented the state of Ohio in the United States Senate from 1974 to 1999.

He was honored with a Congressional Space Medal of Honor in 1978 and was inducted into the Astronauts Hall of Fame in 1990. In 1998 he became the oldest person to fly in space and the only person to fly on both the first and the most recent US space program (Mercury and Shuttle programs) when, at the age of 77, he flew aboard the Space Shuttle Discovery (STS-95). Glenn and M. Scott Carpenter are the last surviving members of the Mercury Seven.