Ian McKellen shared a touching tribute to his best friend and “X-Men” co-star Patrick Stewart, who died on Wednesday at age 86, leaning on their close longtime friendship and his “love” for the fellow English actor.

“Before everything else, Patrick was defined by being born and bred in Yorkshire, the proud county in the north of England which he loved to the end,” McKellen shared in a lengthy, heartfelt post to Instagram Wednesday, alongside a photo of Stewart in his post as Emeritus Chancellor of the University of Huddersfield.

“You could hear it in his accented voice and in the stern honesty with which he told you what he thought and felt. Yorkshiremen have no truck with half-truths or avoidance of big issues. He wore his heart on his sleeve, which made him a man to rely on, to admire and in my case, love.”

“We first met as ambitious young actors with the Royal Shakespeare Company half a century ago but we weren’t in the same productions. My first strong memory was a few years later, meeting him in the street in central London when he told me about an offer to take over a leading part in ‘Star Trek’,” he continued.

“He took the risk and thank goodness for us all that he did for not just his devoted Trekkies but film and theatre audiences, who marvelled at his using international celebrity to star in a string of cinema successes (‘X-Men’ of course) and in great classical plays by Shakespeare, Ibsen, Arthur Miller, Peter Shaffer, Pinter and Beckett at Stratford-upon-Avon, in London’s West End and on Broadway.”

“America was his adopted home, where he met his adored [wife] Sunny who has cared for him through sickness and health, through thick and thin,” McKellen stressed. “But he never forsook his origins: and the proudest achievement of the most respected and beloved actor of his generation on either side of the Atlantic, was his appointment as Chancellor of Huddersfield University in Yorkshire.”

Stewart and McKellen met in the 1970s while working with the Royal Shakespeare Company, both performing in the production of “Every Good Boy.”

However, they didn’t form a close bond until starring in the “X-Men” franchise as super-powered enemies-turned-rivals Professor Charles Xavier and Magneto, respectively.

They both appeared in 2000’s “X-Men,” 2003’s “X2: X-Men United,” 2006’s “X-Men: The Last Stand,” 2013’s “The Wolverine” and 2014’s “X-Men: Days of Future Past.”

The pair will also be in “Avengers: Doomsday” in December, which marks Stewart’s final on-screen appearance.

In 2020, Stewart explained how his and McKellen’s friendship began on the set of “X-Men.”

“We had adjoining trailers,” he said in a “Wired” interview. “On those kind of movies, you spend more time sitting in your trailer than you do in front of the camera.”

“So, Ian and I hung out together, drinking tea — and maybe in the afternoon, something a little stronger — and we got to know one another.” 

Stewart said “the charm” of their bond was realizing the British actors “had so much in common.”

“And by the way, he married us, my wife and me,” Stewart said, referring to his 2013 wedding to singer Sunny Ozell. “He performed the ceremony.” 

Stewart and McKellen showcased their friendship in a 2013 Interview magazine piece, which coincided with their Broadway run in “Waiting for Gadot” and “No Man’s Land.”

In 2016, Stewart described his bond with McKellen as a “love affair.”

“What I love about Patrick is that he’s so predictably myself,” McKellen said at the time in the same interview. “I think we are the same person. If Patrick comes into a rehearsal room and says, ‘Look, look…’ I know what it’s going to be about.”

In his 2023 memoir “Making It So,” Stewart revealed that McKellen tried to stop him from playing Captain Jean-Luc Picard in “Star Trek: The Next Generation.”

“When I told him I was going to sign the contract, he almost bodily prevented me from doing so,” Stewart wrote. “‘No! No, you must not do that. You must not. You have too much important theater work to do. You can’t throw that away to do TV. You can’t. No!’”

Stewart explained that he told his pal he felt he could do theatre again later in his career, while an offer for a role in a hit American TV series “might never come again.”

The “Logan” actor also noted in his book that “there are few people, particularly with regard to acting, whose counsel I trust more than Ian’s.”

Stewart died at his Los Angeles home on Wednesday following a brief battle with Alzheimer’s Disease and Lewy Body Dementia.

He was in the “loving care” of his wife at the time of his passing.

Marvel Studios paid tribute to Stewart by highlighting his role as Professor X.

“For more than 25 years, he brought a gravitas and profundity to the role, earning fans across the globe and helping to transform Super Hero storytelling forever,” the studio said.

Hugh Jackman, who played Wolverine in the superhero franchise, called Stewart “one of the greats of stage and screen today” in his tribute.

“I learned so much from him,” Jackman added. “I will miss you, Patrick Stewart, all of my days.”

In Stewart’s final interview, just three months before his passing, he declared there were “fewer and fewer available roles” for actors as they age.

However, Stewart insisted he wasn’t ready to give up his career.

“I still continue to receive interesting offers and I love being challenged by new work,” Stewart said. “I can’t imagine ever officially ‘retiring.’ I’ll always and forever be an actor.”