William Bosi

William Bosi (born 27 December 1998) is a Scottish professional rock climber specializing in sport climbing, bouldering and competition climbing. Bosi was the first climber to have completed five boulder problems including Alphane in 2022, Burden of Dreams in 2023, Return of the Sleepwalker and Spots of Time in 2024 and Realm of Tor'ment in 2025. Bosi is the first British climber to climb a 9b+ sport climb (Excalibur).

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 (a competition climbing event for boys aged 11 to 13) and also the Scottish Youth Climbing Champion. That year, he also created Honey Badger in the English peak district, which he graded at . 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. 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. King Capella – Siurana (ESP) – March, 2021. First ascent, which Bosi felt was at 9b+, but the grade was settled at 9b after repeats by Alex Megos (2021), and Jakob Schubert (2021).

La Capella – Siurana (ESP) – February, 2020. Third repeat of Adam Ondra's 2011 route, and the second-ever British climber to climb a 9b route (after Steve McClure with Rainman in 2017); sometimes considered closer to 9a+. Free at Last – Dumbarton Rock (GBR) – July, 2022. First ascent. A long-standing unsolved line beside Dave Cuthbertson's famous 1983 route, Requiem (E8 6c), and Dave MacLeod's 2006 equally notable route, Rhapsody (E11 7a); Free at Last became Scotland's hardest route.

Brandenburg Gate – Raven Tor (GBR) – November, 2021. First ascent. The line was regarded as a "holy grail" of British sport climbing.

Mutation – Raven Tor (GBR) – October, 2021. First repeat of Steve McClure's ground-breaking 1998 route, which Bosi suggested was "at least" 9a+ (and possibly harder), making it one of the first-ever 9a+ sport climbing routes in history.

First Ley – Margalef (ESP) – February, 2021. Repeat ascent of Chris Sharma's 2010 route that is popular with aspiring 9a+ climbers.

Boulder problems Return of the Sleepwalker – Red Rock Canyon (US) – February 2024 – First repeat of the world's second-ever V17 boulder problem by Daniel Woods (2021). Bosi practiced on a replica 3D version in Britain.

Alphane – Chironico, (SUI) – October, 2022. Second repeat of Shawn Raboutou's route that Bosi felt was easier than Honey Badger.

Spots of Time – Helvellyn, (En) – October, 2024. First repeat of Aidan Roberts's route.

Realm of Tor'ment – Ravens Tor, (UK) – May 11, 2025. Will's first v17 FA. Por do Sol – Sintra, Portugal, (PT) – January, 2026. First ascent and the hardest boulder in Portugal. Ephyra – Chironico, (SUI) – November, 2022. Third repeat of Jimmy Webb's 2019 boulder.

Honey Badger – Peak District, (GBR) – August, 2022. First ascent and the third British boulder to be graded at V16. Dreamtime – Cresciano, (SUI) – December, 2022. Repeat of the famous boulder Fred Nicole route; took only 4 attempts.