Derek Geoffrey Hersey (26 October 1956 – 28 May 1993) was a British rock climber who specialized in free soloing, and was for many years an active participant in the Boulder, Colorado climbing scene in the United States.

[1][2][3][4] Originally from Stretford, Greater Manchester, England, Hersey was based in Colorado, US, and referred to Eldorado Canyon as his 'office', where he could be seen on any day of the week,[2][5] if not on a road trip to Yosemite National Park or elsewhere.

In 1983, after being unemployed for five years in England, Hersey decided to travel to the United States, where he lived for the rest of his life.

[5] Among them was his free-solo ascent of Crack of Fear, a sustained 5.10+ off-width route at Lumpy Ridge, Colorado;[citation needed] and an impressive effort on the Diamond (a 275-metre (902 ft) wall on Longs Peak), when he free-soloed ascents of two routes and downclimbed another in a single day.

Derek Hersey died on 28 May 1993 in an accident while soloing the Steck-Salathé Route without protective gear, on Sentinel Rock in Yosemite National Park.