Johnson, 26, who has competed in the Winter X Games, was skiing with a group of friends when he fell while trying to negotiate a "very, very tight, rocky area," said Jim Rogers, a member of the Lake Tahoe-area resort's ski patrol.
He fell face-first, then spun around and struck the back of his head on rocks in the Light Towers area of the resort. Johnson was wearing a helmet, but Rogers said the helmet took a serious blow.
Ski patrol members were called shortly before 2 p.m. but were unable to revive him. Placer County Sheriff's Lt. Jeff Ausnow said Johnson died on the slopes.
Johnson was well-known at Squaw Valley, a challenging resort near Lake Tahoe's north shore that hosted the 1960 Winter Olympics. It also is the home base for several members of the U.S. ski team, including Olympic alpine medalist Julia Mancuso.
She tweeted about Johnson's death late Wednesday: "crazy day just got a little bit more unexpected... just learned that my friend and insane skier CR Johnson just died at Squaw.. my heart and prayers go out to everyone at home and CR's family."
Olympic snowboarder Louie Vito also tweeted his reaction: "RIP to my homie CR Johnson. He will be missed by EVERYONE. At least he was doin what he loved but CR YOU WILL NEVER BE FORGOTTEN!!!"
Johnson's father was an avalanche forecaster at the resort for about a decade, Rogers said. The younger skier also had rebounded from a serious injury suffered during a competition in 2005 that put him in a coma for several months.
"This is a man of very, very strong skiing talent," Rogers said. "This young man had been a fixture here at Squaw Valley for years. ... He grew up at Squaw Valley."
A statement from Squaw Valley USA described Johnson as a professional skier and member of its Freeride team.
He also competed in superpipe and halfpipe skiing at events such as the X Games. A photograph on his MySpace page said he was "X-qualified" for a skiing competition in France in 2002, while the Web site for the Ski Channel Television Network said he had been nominated for male skier of the year in 2002.
The freeskier.com Web site posted clips of Johnson in several extreme skier movies, jumping off cliffs and sailing through fresh, untracked powder. One clip includes Johnson talking about relearning to use his arms and legs after a severe injury caused by a collision with another skier while filming at Utah's Brighton ski resort in 2005.
He recalls "being one of the best skiers in the world, overly confident in your skiing, overly confident in yourself. ... Right now I'm working as hard as I possibly can to return to the sport that nearly killed me."
Squaw Valley attracts expert skiers and is known for its difficult terrain. Johnson is the fifth skier to die on the slopes over the past three years. Two of the five died in avalanches, including one member of the ski patrol.
Attempts to reach Johnson's family late Wednesday were unsuccessful, and a telephone message left with a spokesman for the X Games was not immediately returned.
Johnson, whose first name was Charles, had posted the following statement his MySpace page: "I feel it's most important to keep it real and enjoy each moment, you know, take advantage of every opportunity life provides, because who knows what tomorrow may bring."