Patrick Stewart, the classically trained stage actor who became a blockbuster star through the “Star Trek” franchise and the “X-Men” films, has died at 86. His career stretched from acclaimed theater performances to two of his most widely known screen roles.

Stewart died Wednesday in Los Angeles, according to spokesperson Kelly Bush Novak. Novak said the actor died following “a brief and poignant journey” with Alzheimer’s disease and Lewy body dementia, as reported by News Nation Now.

For generations of viewers, Stewart was best known as Professor Charles Xavier and Captain Jean-Luc Picard. Those characters placed him at the center of the “X-Men” films and the “Star Trek: The Next Generation” series and films, respectively.

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Despite the enormous visibility of those performances, Stewart spent more of his career onstage than he did in the X-Mansion or aboard the USS Enterprise. Theater remained a substantial part of his professional life before and after mainstream fame arrived.

Stewart became an actor at age 18. Beginning in the 1960s, he gained acclaim onstage as a member of the Royal Shakespeare Company, building a career rooted in classical performance long before his best-known screen work.

His path to widespread fame did not accelerate until he was hired for “Star Trek: The Next Generation” at age 47. The role of Captain Jean-Luc Picard transformed Stewart into a mainstream star and remained central to his public profile.

Stewart continued acting into his 80s. His lengthy career therefore encompassed his early work as a young actor, decades of celebrated stage performances, and the franchise roles that made him familiar to audiences beyond the theater.

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Onstage, Stewart played roles ranging from Claudius to Macbeth. His theatrical work reflected the classical training that defined the beginning of his career and continued to occupy more of his professional life than his time in either major screen franchise.

He also frequently performed a solo rendition of “A Christmas Carol.” The production became another recurring part of a stage career that was not confined to ensemble productions or the characters most closely associated with his film and television success.

Stewart appeared in West End and Broadway runs of Harold Pinter’s “No Man’s Land” and Samuel Beckett’s “Waiting for Godot.” He performed the plays in repertoire with his friend Ian McKellen.

The two actors shared the stage while Stewart remained closely identified with Professor Charles Xavier and Captain Jean-Luc Picard. Those theater appearances demonstrated how his stage work continued alongside the screen performances that had brought him mainstream recognition.

In 2010, Stewart was knighted by the Queen at Buckingham Palace, becoming Sir Patrick Stewart. The honor placed him in the company of British actors he had long regarded as professional heroes.

Stewart told reporters that those heroes were Laurence Olivier, John Gielgud and Alec Guinness. All three had also been knighted, a connection Stewart described as deeply meaningful to him.

Speaking about the honor, Stewart said being “in that company is the grandest thing that has professionally happened to me.” The statement captured the importance he placed on joining the ranks of the admired British performers who had preceded him.

Away from his acting career, Stewart was married three times and had two children. His third marriage was in 2013 to American musician Sunny Ozell.

His death closes a career that began when he was 18, brought stage acclaim through the Royal Shakespeare Company beginning in the 1960s, and reached mainstream audiences after “Star Trek: The Next Generation.” The Associated Press and Reuters contributed to the report.