William Bosi
William Bosi is a Scottish professional rock climber specializing in sport climbing, bouldering and competition climbing. Bosi is only the second British sport climber in history to redpoint a graded sport climbing route, and by 2023, was one of only a small group of climbers in the world to have completed a boulder. In 2025, he made a redpoint ascent of the sport climb Excalibur, which is graded 9b+, making him the first British climber to climb at this grade.
Early life and education
Bosi was born in Edinburgh to Alison and Martin Bosi. His mother is a nursery nurse from Inverleith, Scotland. Both parents took him and his 3-year-old brother Alexander to an indoor climbing centre in Newhaven, Edinburgh when he was 6 years old. He attended Broughton High School, Edinburgh. By 2011, Bosi was the British Champion in the Youth Climbing Series and also the Scottish Youth Climbing Champion.Climbing career
Sport climbing
In 2016, Bosi came to attention when aged 17 he redpointed Steve McClure's famous British sport climbing route Rainshadow, becoming the youngest Briton to climb a graded sport route.In 2020–2021, Bosi became only the second British climber in history, after Steve McClure, to climb a grade sport route with his repeat of Adam Ondra's La Capella, and followed up by his first free ascent of King Capella, both of which are in Siurana in Spain.
Bouldering
In 2022, on a trip with Adam Ondra to his home crag of Moravský Kras in the Czech Republic, Bosi flashed the boulder, Charizard. That year, he also created Honey Badger in the English peak district, which he graded at.In November 2022, Bosi became one of only a handful of boulderers in the world to have climbed a grade boulder when he repeated Shawn Raboutou's Alphane, which he felt was easier than his own 8C+ graded route, Honey Badger. In April 2023, he made the first repeat of Nalle Hukkataival's Burden of Dreams, considered the world's first-ever boulder, and which at the time of Bosi's repeat was still considered the world's hardest boulder. In February 2024, Bosi made the first repeat of Daniel Woods' Return of the Sleepwalker, which he felt was easier than Burden of Dreams, but harder than Alphane, with Bosi stating that Woods' route was definitely at a V17 grade. In October, Bosi repeated Aidan Roberts' Spots of Time 9A, confirming the grade and making it the first 9A boulder in the United Kingdom. This made Bosi the first to climb four confirmed 9A boulders.
Competition climbing
Bosi has represented Britain in competition lead climbing, in both youth and adult formats, and in 2018 became the first Briton to reach an International Federation of Sport Climbing final in 30 years, where he finished fifth at the IFSC World Cup in Chamonix; he finished fourth twice during the 2019 IFSC World Cup. Bosi narrowly missed out on a place in the Tokyo 2020 Olympics, despite trying to learn speed climbing, a required discipline in Olympic competition climbing.In 2021, Bosi announced that he was taking a break from competition climbing to focus on outdoor sport climbing and bouldering.