Garrett Madison (born November 3, 1978) is an American mountaineer and guide. Madison began guiding professionally in 1999 on Mount Rainier, and his company, Madison Mountaineering, specializes in climbs on Mount Everest and other high altitude peaks, operates on the highest peaks on all seven continents, and also provides training programs and summit climbs in Washington State. On May 19–20, 2011, he reached the summit of Mt Everest on his fourth successful attempt as expedition leader and guide for Alpine Ascents International, and reached the summit of Lhotse (the fourth highest mountain in the world) 21 hours later as guide to climber Tom Halliday. Also on the expedition was guide Michael Horst who made both summits as well in under a 24-hour period, a few days earlier. This was the first time that both Everest and Lhotse were summited together in less than 24 hours, and Madison repeated the "double header" feat again in 2013, the only person to do so twice. In 2014, Madison led the first successfully guided ascent of K2, reaching the summit with two climbers and three Sherpas on July 27, 2014. On 22 July 2018, Madison successfully led a team of 24 to the summit of K2 and became the first American to summit K2 more than once. Madison also regularly guides many "7 Summits" expeditions such as Carstensz Pyramid, Aconcagua, Vinson Massif, Kilimanjaro and Elbrus during the year.