Walter Marvin Koenig, born September 14, 1936, in Chicago, Illinois, is an American actor and screenwriter best known for portraying Pavel Chekov in Star Trek: The Original Series and Alfred Bester in Babylon 5.

     Koenig grew up in New York City, where his family had moved when he was a child. His parents were Russian Jewish immigrants, and his father was investigated by the FBI during the McCarthy era. He attended Grinnell College before transferring to UCLA, where he earned a Bachelor of Arts in Psychology. Encouraged by a professor to pursue acting, he later studied at the Neighborhood Playhouse School of the Theatre alongside Christopher Lloyd and James Caan.

     His early career included roles in The Lieutenant (1963–64) and The Alfred Hitchcock Hour (1964). In 1967, he was cast as Ensign Pavel Chekov, the navigator of the USS Enterprise, in Star Trek: The Original Series. He reprised the role in six Star Trek films and later voiced President Anton Chekov in Star Trek: Picard (2023).

     Beyond Star Trek, Koenig played Psi-Cop Alfred Bester in Babylon 5, appearing in 12 episodes. He also starred in Moontrap (1989), The Questor Tapes (1974), and Goodbye, Raggedy Ann (1971). As a writer, he contributed to Land of the Lost, Family, and The Powers of Matthew Star. He authored several books, including Warped Factors: A Neurotic's Guide to the Universe and Chekov's Enterprise.

     Koenig was married to Judy Levitt from 1965 until her passing in 2022, and they had two children, including Andrew Koenig, who tragically passed away in 2010.