Dunk's new contract will expire in the summer of 2026.
The 31-year-old has been with Brighton since he was a school boy and has made 416 appearances to date.
Dunk's journey with Brighton started in League One and he has played an immense role in helping the Seagulls get established in the Premier League.
Last season, Dunk missed just two Premier League games as Brighton finished sixth and qualified for the Europa League for the first time in their history.
He was named captain in 2019.
A club statement read: "We are pleased to announce that Lewis Dunk has signed a new contract that runs until June 2026.
Brighton manager Roberto De Zerbi added: “Long live the captain!
“I’m really happy he has signed this new contract. It’s good news for Lewis and the club.”
Lewis has one cap for England but missed the chance to make more appearances for his country when injury ruled him out of European Championship qualifiers against Malta and North Macedonia last month.
