The Leadville Race Series is a family of high-altitude endurance races based in Leadville, Colorado, a former silver-mining town sitting at 10,152 feet. It began in 1983, when 45 runners set out on a 100-mile course through the surrounding Rocky Mountain terrain. That race became the Leadville Trail 100 Run, nicknamed the Race Across the Sky, and the series has since grown into a slate of mountain bike and trail running events at distances from 10K to 100 miles.

The series is owned and produced by Life Time, Inc. Its Colorado events run from June through August each year: the Leadville Trail 100 MTB, the Leadville Trail 100 Run, the Silver Rush 50 MTB and Silver Rush 50 Run, the Leadville Trail Marathon and Heavy Half, the Leadville 10K, and the three-day Leadville Stage Race. Life Time also produces the Austin Rattler weekend at Reveille Peak Ranch in Burnet, Texas, which serves as an official qualifier for both 100-mile flagship races.

Entry into the two 100-milers is not first-come, first-served. Riders and runners get in through a lottery that opens December 1-15 for the following August, through a training camp or coaching package, through a charity partner slot, or by earning one of the qualifier coins awarded at designated qualifier races (a minimum of 35 coins are distributed at each qualifier, by a mix of performance ranking and lottery draw). Registration for the Colorado races typically opens in January.

Exact dates, pricing, and qualification rules for each season are published at leadvilleraceseries.com.