Walter Koenig, who portrayed the enthusiastic Russian navigator Ensign Pavel Chekov on the original "Star Trek" television series and subsequent films, has died at age 90.

Koenig died of old age Sunday night at his home in the North Hollywood neighborhood of Los Angeles, surrounded by his daughter and niece, according to a statement from his representative Zachery McGinnis.

Born Sept. 14, 1936, in Chicago to Russian Jewish immigrants, Koenig joined the "Star Trek" cast in its second season in 1967. He appeared in 36 of the show's 50 original episodes through 1969 and reprised the role in six feature films from 1979 to 1991. His Chekov character, introduced partly to appeal to younger viewers, often provided comic relief with his accent and claims attributing inventions to Russia.

Beyond "Star Trek," Koenig played the telepath Alfred Bester on the science fiction series "Babylon 5" in the 1990s. He also worked as a writer, contributing scripts to shows including "Land of the Lost" and "The Incredible Hulk," and authored books such as the memoir "Warped Factors." In recent years, he voiced a character in a 2023 episode of "Star Trek: Picard" and earned the Platinum Award for Best Actor at the 2026 Independent Shorts Awards for his role in the short film "Mr. Fleischmann."

Koenig was married to actress Judy Levitt from 1965 until her death in 2022. Their son, actor Andrew Koenig, died by suicide in 2010 at age 41. He is survived by their daughter, Danielle Koenig.

Tributes poured in from co-stars and fans. George Takei, who played Hikaru Sulu, posted on social media that he and Koenig remained friends for nearly six decades and that Koenig served as best man at Takei's 2008 wedding. "Walter was more than Chekov. He was a writer, a teacher, a thoughtful man, and a loyal friend," Takei wrote.

Koenig's death leaves William Shatner and Takei as the only surviving main cast members from the original series. His representative's statement noted that Koenig's legacy extended through convention appearances and his engagement with fans, adding that he "understood what Star Trek meant to people and embraced the community that grew around it."