Bowen's new deal will take him through to the summer of 2030.
His previous contract would have expired in 2025.
Bowen joined the Hammers in January 2020 for an initial £18m from Hull City and has scored 45 goals in 166 appearances for David Moyes' side.
The 26-year-old cemented his place in West Ham folklore when he scored the winning goal in the Europa Conference League final against Fiorentina last season.
“I’m so pleased to have signed a new long-term contract at West Ham,” Bowen told the club website.
“Everyone knows what this club means to me, so committing my future until 2030 means so much to me and my family.
“I’ve loved every minute of my time here. Winning the Europa Conference League in Prague was an amazing moment, scoring the winner in the last minute will be something I’ll cherish forever.
“It’s left us all wanting that feeling again and again – we want to create more memories together, for our fantastic fans, and for this fantastic football club.”
Bowen has scored five goals in eight Premier League appearances this season, earning him a recall into Gareth Southgate's squad for England's upcoming international games against Australia and Italy.
