Walter Koenig, the actor best known for his role as Ensign Pavel Chekov in the original 1960s “Star Trek” television series, has died at the age of 90. He passed away Monday at his home in the North Hollywood neighborhood of Los Angeles, surrounded by his daughter and niece, according to his talent agent, Zachery McGinnis.

Koenig portrayed the young Russian navigator aboard the USS Enterprise, joining the series at the start of its second season in 1967. The character was introduced by creator Gene Roddenberry to appeal to younger viewers, serving as a youthful counterpoint to the lead actors William Shatner and Leonard Nimoy, who were in their mid-30s when the show began. Koenig, 30 at the time of casting, was given a distinctive mop-top hairstyle, inspired by popular music groups of the era, to enhance his character’s appeal to a teenage audience. Chekov’s role also symbolized a future of international cooperation during the Cold War, depicting a Russian officer working alongside a captain from Iowa as humanity explored space together.

Born Walter Marvin Koenig on September 14, 1936, in Chicago to Lithuanian Jewish immigrant parents, he grew up in Manhattan’s Inwood neighborhood. He initially pursued studies in psychology before turning to acting, eventually making his television debut in the early 1960s with roles on various series such as “Combat!,” “The Alfred Hitchcock Hour,” and “The Lieutenant,” which was created by Roddenberry and helped lead to his “Star Trek” casting.

Koenig appeared in 36 episodes of the original series from 1967 to 1969 and reprised his role as Chekov in seven “Star Trek” feature films released between 1979 and 1994. He also authored a book about the series titled *Chekov’s Enterprise* in 1980. Beyond “Star Trek,” Koenig maintained a steady career in television, including a notable role in the 1990s science-fiction series “Babylon 5” as the telepathic officer Alfred Bester.

Friends and colleagues paid tribute to Koenig’s legacy and friendship, with fellow castmate George Takei, who played Lieutenant Hikaru Sulu, remembering him as “more than Chekov” — a writer, teacher, and loyal friend. Koenig served as best man at Takei’s 2008 wedding, highlighting their close bond of nearly six decades.

Koenig’s personal life included marriage to actress Judy Levitt in 1965, who appeared alongside him in several “Star Trek” films and who died in 2022. They had two children: Danielle Koenig, an actress, and Andrew Koenig, also an actor, who died in 2010.

Although Koenig initially had low expectations for “Star Trek” — he once remarked on the show’s early special effects as unconvincing — the series and its fandom grew into a significant cultural phenomenon. He acknowledged the passion of the fans, known as Trekkies, describing them as people drawn by a sense of humanity, justice, and imagination.

Koenig’s death leaves William Shatner and George Takei as the last surviving main cast members of the original “Star Trek” series.