Walter Koenig, who was best known for playing the Russian crewman Pavel Chekov in the original Star Trek TV series, has died at the age of 90.

The US actor passed away on Sunday (25 October) of natural causes in his home in North Hollywood, according to a statement from his talent agent, Zachery McGinnis.

“Walter’s legacy extends far beyond the screen. Through countless convention appearances and interactions with fans, he shared his kindness, wit, and appreciation with everyone fortunate enough to meet him. He understood what Star Trek meant to people and embraced the community that grew around it,” the statement read.

“Thank you, Walter, for the memories, the inspiration, and for boldly going where few have gone before.”

Born in Chicago in 1936, Koenig initially studied psychology at university before turning to acting, training at New York’s Neighborhood Playhouse School of the Theatre.

His earlier roles included guest appearances in 1960s TV series such as Combat!, The Untouchables, Ben Casey, Gidget and I Spy, but it was Star Trek in 1967 that served as his big break.

The original series ran on NBC for three seasons between 1966 and 1969 and grew into a cultural phenomenon, leading to more than a dozen spin-off shows, more than a dozen movies and enthralling a large fandom for more than six decades.

Koenig appeared in the sci-fi franchise as the navigator of the starship USS Enterprise in the second and third seasons between 1967 and 1969, before later reprising his role in all six original-cast Star Trek films.

Other notable roles included as Alfred Bester in another sci-fi space series, Warner Bros Television’s Babylon 5, from 1994 to 1998.

“My heart is heavy,” Koenig's co-star, George Takei, said in a post on X.

Takei, who played Hikaru Sulu in the franchise, added: “Walter was more than Chekov. He was a writer, a teacher, a thoughtful man, and a loyal friend.”

Koenig married Judy Levitt, who starred alongside him in three Star Trek movies and in Babylon 5, in 1965. They were together until her death in 2022.

The actor is survived by their daughter, the actress and screenwriter Danielle Koenig (Star vs the Forces of Evil).