Sir Patrick Stewart, the commanding British actor who brought Captain Jean-Luc Picard to life across three decades of "Star Trek" and gave the X-Men their moral center as Professor Charles Xavier, has died at 86.

Stewart died Wednesday at his home in Los Angeles, according to a statement posted to his official social media accounts. The post said he died after a "brief and poignant journey" with Alzheimer's disease and Lewy body dementia. He is survived by his wife, musician Sunny Ozell, and his children, Daniel and Sophie.

Born in Mirfield, Yorkshire, in 1940, Stewart spent decades honing his craft with the Royal Shakespeare Company before global fame found him in 1987, when he was cast as the bald, imperious, endlessly humane captain of the USS Enterprise in "Star Trek: The Next Generation." The role made Picard one of science fiction's most enduring figures and carried Stewart through seven television seasons, four feature films and a late-career revival, "Star Trek: Picard," that let him close out the character on his own terms.

He found an entirely different kind of stardom playing Professor X, the telepathic founder of Xavier's School for Gifted Youngsters, across more than half a dozen "X-Men" films starting in 2000 — a role that introduced him to a generation of fans who had never seen a starship. CBS News noted that the two franchises, running in parallel for much of his career, made Stewart one of the rare actors beloved equally by two separate fandoms that rarely overlapped.

Tributes poured in from both worlds

Hugh Jackman, who played Wolverine opposite Stewart's Professor X for nearly two decades, wrote on Instagram that the world had lost "one of the greats of stage and screen." William Shatner, who originated the captain's chair Stewart would later occupy in his own era of "Star Trek," called it a "heartbreaking week" and said Stewart "brought intelligence, grace and humanity to everything he did."

HE BROUGHT INTELLIGENCE, GRACE AND HUMANITY TO EVERYTHING HE DID.

Stewart was knighted in 2010 for his services to drama, capping a stage career that included a Tony-nominated solo "A Christmas Carol" and acclaimed turns in "Macbeth" and "Waiting for Godot" alongside Ian McKellen, his frequent collaborator and close friend both on stage and in the "X-Men" films. He was open in later years about his advocacy work, including decades spent as a patron of Refuge, a UK domestic violence charity, following his own childhood experience of witnessing domestic abuse.

Per Variety's obituary, Stewart continued working steadily into his 80s, including voice work and guest appearances, and had spoken publicly in recent years about aging gracefully in an industry obsessed with youth. Friends and colleagues described him as warm and unpretentious off-camera, a counterpoint to the authority he projected in his two signature roles.

No funeral details had been announced as of Friday morning. Fans gathered informally outside TCL Chinese Theatre in Hollywood on Thursday night, leaving flowers near Stewart's star on the Walk of Fame, which he received in 2015.