The 86-year-old died at his home in Los Angeles on Wednesday, said a statement on his Instagram account.
The West Yorkshire actor achieved global fame playing Captain Jean-Luc Picard in Star Trek: The Next Generation in 1987, which ran for seven years.
He also played Professor Charles Xavier in multiple X-Men films, beginning with the original in 2000, and recently appeared in a trailer for Avengers: Doomsday.
Sir Patrick was also a veteran of the stage, appearing in the West End and Broadway, and was nominated for a Tony Award for his much-praised take on Macbeth.
Marvel Studios called him “a singular talent, a generous collaborator, and a true gentleman”.
It said he brought the Professor X character to life with “extraordinary grace, intelligence, and humanity, defining the character for generations of fans”.
Star Trek actor William Shatner was also among the first to pay tribute, calling Stewart “a magnificent actor” who would be “deeply missed”.
“He brought intelligence, grace, and a deep sense of humanity to everything he did,” Shatner wrote on X.
“Captain Picard stood for the best of us, and so did the man who played him. I was filled with affection and admiration for him and his work.”
Wolverine star Hugh Jackman said the acting world had “lost one of the greats” and a “tremendous friend and man”,
“I learned so much from him. I will miss you, Patrick Stewart, all of my days,” Jackman wrote.
Stewart’s family said he died “in the loving care of his beloved wife Sunny, following a brief and poignant journey with Alzheimer’s Disease and Lewy Body Dementia”.
They said he was surrounded by “live music, prayer, tears, laughter” during his illness.
“We will forever cherish the peaceful ease and reflection on his face, an enduring reminder of his invincible grave,” a statement said.
His family also paid tribute to his time with the Royal Shakespeare Company, appearances on Broadway, and his love of Huddersfield football club.
They said his acting career was matched by his philanthropy and campaigning on issues such as domestic violence, veterans’ mental health services, and animal welfare.
He was knighted by the Queen in 2010 for his services to drama.
This breaking news story is being updated and more details will be published shortly.
Please refresh the page for the fullest version.
You can receive breaking news alerts on a smartphone or tablet via the Sky News app. You can also follow us on WhatsApp and subscribe to our YouTube channel to keep up with the latest news.
