His publicist, Bumble Ward, said that his death had been unexpected and that the cause was a heart attack. Mr. Vallée was found on Sunday by friends who were going to visit him, said Lt. Benoit Richard, a spokesman for the Sûreté du Québec Police Department. Further details were not immediately available.
Mr. Vallée was known for a naturalistic and generous approach to filmmaking that colleagues said brought out the best in those he worked with. He avoided artificial lighting — and even rehearsals. Mr. Vallée also became known for directing several films and television series with strong female leads.
His first feature film, “Liste Noire” (“Black List”), a 1995 thriller that follows the trial of a judge, was nominated for several Genie Awards, the Canadian equivalent of the Oscar, including for best picture. Ten years later, he directed and co-wrote “C.R.A.Z.Y.,” a coming-of-age film, whose success helped catapult him to Hollywood.
In 2009, Mr. Vallée directed “The Young Victoria,” starring Emily Blunt, which explored the early years of Queen Victoria’s rule. The film received several major awards and nominations.
He was best known for the critically acclaimed “Dallas Buyers Club” (2013), a drama based on the true story of Ron Woodroof, a Texas electrician and rodeo rider who, after receiving a diagnosis of H.I.V. in 1985, fought to get medication (illegal in the United States at the time) for himself and others with the virus.
Matthew McConaughey, who played Mr. Woodroof, said he dropped 50 pounds by ingesting nothing but vegetables, egg whites, fish and tapioca pudding — and “as much wine as I wanted to drink.” The film was nominated for six Oscars, winning three, including best actor for Mr. McConaughey and best supporting actor for Jared Leto.
In a recent Vanity Fair article adapted from the book “Never Silent: ACT UP and My Life in Activism,” the activist Peter Staley recounted his long battle to make sure homophobia and AIDS denialism did not make it into the film. He said that he put Mr. Vallée “through hell and back,” but that the director “kept the promise he’d once emailed me: that in all his films, he tries to ‘capture humanity and reveal the beauty behind it.’”
The next year, Mr. Vallée directed “Wild,” also based on a true story, which starred Reese Witherspoon as the author Cheryl Strayed during a solo hike on the Pacific Crest Trail. That film was also nominated for several major awards, including an Oscar nomination for best actress.
“Big Little Lies” won several Emmys and an award from the Directors Guild of America. A cutting tale of violence and class in the wealthy beachside town of Monterey, Calif., it starred Ms. Witherspoon, Nicole Kidman, Zoë Kravitz, Laura Dern, Shailene Woodley and Meryl Streep.
Mr. Vallée later directed the HBO mini-series “Sharp Objects,” set in small-town Missouri, which starred Amy Adams as a troubled reporter. It was nominated for eight Emmy Awards.
“It’s true that my last projects were featuring mainly female characters,” Mr. Vallée said in an interview published by HBO in 2018. “So, am I the lucky guy? Maybe — maybe I am. I’m not afraid of intelligent, strong women. You got to create a space where they’re going to feel respected and comfortable.”
“We pushed the envelope in order to capture something that feels real and authentic,” he added. There were no storyboards, shot lists or reflectors used in making “Sharp Objects” because he preferred to allow the actors to express themselves.
“I’m reacting to what they’re doing, instead of being active and telling them, this is what I’ll do with the camera,” he said, adding: “I love it. You know, I’m like a kid on a set, a kid playing with a huge toy and having fun.”
Mr. Vallée was born on March 9, 1963, in Montreal. He studied filmmaking at the Collège Ahuntsic and the University of Quebec in Montreal. He is survived by two sons, Alex Vallée and Emile Vallée, and his siblings Marie-Josée Vallée, Stéphane Tousignant and Gérald Vallée. His marriage to the writer and actress Chantal Cadieux ended in divorce.
In a statement, Nathan Ross, Mr. Vallée’s producing partner and close friend, described him as a “true artist” who stood for “creativity, authenticity and trying things differently” and added, “It comforts knowing his beautiful style and impactful work he shared with the world will live on.”
Mr. Vallée was set to direct and serve as executive producer of another show for HBO, “Gorilla and the Bird,” a limited series based on a memoir of the same name about a public defender who suffers a psychotic break.
In an interview with The New York Times in 2018, Mr. Vallée described his work as attempting to expose the flaws and imperfection in human nature.
“I see that I seem to be attracted to these stories and to underdog characters,” he said. He added, “The humanity, the beautiful humanity, is dark.”
Johnny Diaz contributed reporting.