He apparently died of "heat-related issues," the local sheriff said, after the 50-year-old's body was found near Zabriskie Point, a famed movie-related panorama spot.
Legeno played the werewolf Fenrir Greyback in several of the "Harry Potter" movies, including "Harry Potter and the Half-Blood Prince" (2009) and the two-part finale "Harry Potter and the Deathly Hallows."
He also appeared in episodes of British soap operas "Eastenders," "The Bill" and "Emmerdale," as well as in films including 2005's "Batman Begins."
Two hikers found Legeno's body on Sunday in a remote area in the center of Death Valley, where summer temperatures regularly top 49 degrees Celsius (120 F).
"The remains have been identified as David Legeno, a 50-year-old United Kingdom man," said the Inyo County Sheriff's Office in a statement.
"It appears that Legeno died of heat-related issues, but the Inyo County Coroner will determine the final cause of death. There are no signs of foul play."
Legeno worked on demolition sites after leaving school, before studying performing arts. He became a professional wrestler before getting a role in Guy Ritchie's 2000 London gangster movie "Snatch."
When film work was slow he earned his living as a professional cage fighter, according to his profile on the IMDb movie industry website, adding that he put his fight career on hold after being in "Harry Potter."
Zabriskie Point is the name of a 1970 movie by Italian great Michelangelo Antonioni, and the spot -- famous for spectacular multi-colored panoramas of Death Valley -- was used for the cover of rockers U2's 1987 album "The Joshua Tree."