Glenn, John H. (Herschel), Jr. (1921-), a United States astronaut and politician. On February 20, 1962, he became the first American astronaut to orbit the earth, in the Mercury space vehicle Friendship 7.

Glenn was born in Cambridge, Ohio. He left Muskingum College in 1942 to become a naval air cadet. He served in the Pacific theater during World War II and in the Korean War. As a test pilot in 1957, Glenn became the first person to fly at supersonic speed from Los Angeles to New York City. He was a lieutenant colonel in the Marine Corps when he was chosen for astronaut training in 1959.

Glenn retired as a colonel in 1964 and became a business executive. He later entered politics as a Democrat and was elected to the U.S. Senate from Ohio in 1974 and reelected in 1980, 1986, and 1992. In 1998, at the age of 77, Glenn retired from the Senate and was selected to be a crew member on a space shuttle mission.

John Glenn: A Memoir was published in 1999.