The bronze-graded Briton will partner Gregoire Saucy, the 2021 Formula Regional European Championship by Alpine champion switching to sportscars after two years in Formula 3, and a yet-to-be announced third driver aboard a McLaren 720S GT3.
His WEC switch means Cottingham will once again battle with Darren Leung, who was announced at the WRT BMW squad last week alongside Augusto Farfus and Sean Gelael, after their season-long tussle for the British GT title in 2023.
Cottingham was narrowly defeated by Leung and Dan Harper after a penalty in the final round at Donington for overtaking under yellow flags demoted the 2 Seas Mercedes he shared with Philip Ellis to tenth, as Leung and Harper's Century BMW secured the crown by storming to second.
Accomplished historic racer Cottingham has previous experience in the 720S from racing for 7TSIX in the 2023 Dubai 24 Hours, and has entered this year's Asian Le Mans Series with Optimum Motorsport with a best result to date of fifth in Sepang.
"It has been a dream of mine since I was a boy to race at Le Mans and compete in a World Championship and after only two and a half years of racing in modern motorsport, I didn’t think I would get this opportunity,” said Cottingham.
"With everything I’ve done over the last two years including British GT, the Gulf 12 Hours, Spa 24 Hours and Dubai 24 Hours, I’m ready for this new challenge.
"I really enjoy driving the McLaren and am totally dedicated to the FIA World Endurance Championship this year."
United Autosports has announced Marino Sato, a race winner in its European Le Mans Series LMP2 team last year, as the first driver for its second entry as McLaren embarks on its maiden season of WEC competition.
The manufacturer was ineligible to enter the WEC previously as it didn't have a car that conformed to the GTE regulations which were phased out at the end of 2023.
United switched to the class that replaces GTE Am after the LMP2 division was dropped from the WEC for 2024 due to the rising number of Hypercar manufacturers.