Summerville, 24, joins Al Hilal on a four-year contract. West Ham are said to receive £65 million (€76 million) for the Dutchman, who made his senior Netherlands debut in the friendly against Algeria ahead of the 2026 FIFA World Cup.
Summerville, a 6-time Netherlands international, has become the third-most expensive sale in West Ham history, behind Declan Rice and Mateus Fernandes, who joined Tottenham Hotspur earlier this summer.
Simultaneously, Summerville has become Al Hilal's second-most expensive incoming transfer in club history. The Saudi record champions' record stands at €90 million, which they paid for Neymar in 2023.
According to Sky Sports' Florian Plettenberg, the 24-year-old is set to earn up to €17 million net per year, making his entire contract worth €68 million.
Roma and Manchester United were reportedly in the race for Summerville, with the Italian side having submitted several bids up to €45 million and coming close to convincing Summerville of the move.
Summerville scored five goals and provided two assists in 31 Premier League games for West Ham during the 2025-26 season. The Dutchman joined the Hammers from Leeds United in 2024 for a reported fee of €29.3 million.
At the World Cup, Summerville impressed with 2 goals and 2 assists in four games (253 minutes).