Furnace Creek 508 was an ultramarathon bicycle race that took place annually each October between 1989 and 2013 in Southern California. Its route started in Santa Clarita (25 miles north of Los Angeles), went northeast to Towne Pass and dropped into Death Valley, traversed Death Valley in the southern direction, crossed Mojave Desert and ended at Twentynine Palms. The race was named after the total length of its course (508 miles) and the location of its midpoint (near Furnace Creek).

Rather than use names or numbers as in other races and other sports, the Furnace Creek 508 identified riders and teams with "totems" - animal names said to signify or have a special meaning for a rider or team.

The race was discontinued in 2014 due to a policy change of the Death Valley National Park that prohibited competitive cycling events in the park. Its organizers have since created a new annual event, the "Silver State 508", which keeps the overall format and the total distance of the course, but takes place in Nevada.

At 508 miles (818 km) of length and 36,000 feet (11,000 m) of elevation gain, the Furnace Creek route was roughly comparable to four typical mountain stages of Tour de France ridden back-to-back.

Until rules changes in 2003, the Furnace Creek 508 was a qualifying event for the Race Across America.