Hong Kong Four Trails Ultra Challenge (), or HK4TUC (), is an annual ultramarathon race in Hong Kong. Considered one of the most challenging mountain races worldwide, participants have to run through within 72 hours the famous quadruple hiking trails in Hong Kong known as "Four Trails": MacLehose, Wilson, Hong Kong, and Lantau. The ultramarathon spans a total distance of 298 kilometres with a cumulative elevation of 14,500 metres, starting from Tuen Mun and ends at the green post box outside Silvermine Bay Ferry Pier in Mui Wo.
History.
The challenge was founded by Andre Blumberg, a German expat living in Hong Kong in 2012 when he decided to run the four trails in four days during the Chinese New Year holiday period. Blumberg later said he decided to challenge himself and get in shape as mid-life crisis loomed. Participation is strictly by invitation from Blumberg, who permitted around two dozens of runners every year. After an overhaul of the system in 2014, two titles of "finisher" and "survivor" are introduced. Runner could only earn the title of "finisher" if complete the four trails within 60 hours, and "survivor" in 72 hours. New rules were implemented to increase the difficulty, with hiking poles banned in 2021, painkillers in 2022, and watches in 2025.
The 2021 race only invited past finishers and survivors amidst the coronavirus pandemic. Prominent runners including Stone Tsang and Tom Robertshaw withdrew during the race, with Jacky Leung making history as the first that breaks the 50-hour mark. "Four Trails", a film that documents that year's challenge, was released in 2025.
Four Trails.
The challenge starts on the first day of the Lunar New Year, which usually falls in January or February. Spanning a total of 298 kilometres, the route has a cumulative elevation of 14,500 metres. Runners had to complete all the routes solo and self-supported with crew support allowed only off-trails. Sleep breaks and rests are allowed but will count into the timing.
The four trails, individually ran in reverse from the finishing point back to the start and in the following sequence, are: 
Records.
The record holder is Wong Ho-chung who achieved a result of 46 hours 55 minutes in 2022. He, along with another local Jacky Leung, are the duo "breaking 50" achievement holders. Nikki Han and Cheung Man-yee are the two only female finisher. The youngest successful participant is Sarah Pemberton, completing the race in 70 hours 45 minutes in 2020 at the age of 26.
Only six runners claimed the "finisher" title twice: Nugo Yamanath Limbu, Jacky Leung, Salomon Wettstein, Hyun Chang Chung, Nikki Han, and Tomokazu Ihara.