Walter Koenig, the stalwart Pavel Chekov who navigated the Starship Enterprise for the better part of six decades of Star Trek, has died at the age of 90.

Koenig, whose parents emigrated from the Soviet Union, joined the Star Trek crew in the second season, adding a Russian character to the bridge at the height of the Cold War. He would go on to play Chekov in six feature films featuring the original series cast and had a voice cameo in Star Trek: Picard in 2023.

He remained close to most of his fellow cast members — William Shatner excepted — especially the person who sat next to him at the helm all those years: George Takei, who played Hikaru Sulu. Fans even shipped the two as Chulu. On Monday, Takei shared a final photo with Koenig on Instagram and offered a touching tribute to his late friend.

"Walter and I met on the bridge of the Enterprise in the 1960s, and we stayed friends for nearly six decades," Takei wrote. "When Brad [Altman] and I married in 2008, Walter stood beside us as our best man. Just last month, on Sept. 14, he turned 90, on the same day Brad and I celebrated our 18th wedding anniversary. I will always treasure that he and I shared that date.

"Walter was more than Chekov," Takei continued. "He was a writer, a teacher, a thoughtful man, and a loyal friend. To the fans who loved him for so many years, thank you. He loved you too.

"Rest well, my dear friend. Keep navigating a steady course."

While the Star Trek films received Academy Award attention for the technical achievements, the cast was overlooked, leaving it up to the genre awards to recognize the actors. For his part, Koenig received Saturn Award nods for the two best Trek films, The Wrath of Khan and The Voyage Home.

Aside from his Trek duties, Koenig was a key player in another sci-fi series, Babylon 5. He also was a writer, working on the Star Trek animated series (after he wasn't asked to reprise Chekov as a cost-saving move, a decision that upset the actor) as well as 1970s shows like Land of the Lost and Family.