The 28-year-old England international center-half made 36 Premier League appearances last season.
“We’re absolutely delighted Lewis has made this long-term commitment to the club,” said head coach Graham Potter.
“He’s been a joy to work with and he’s a top player. He leads by example on the pitch and he’s a good lad off it. We’re very lucky to have him.”
Lewis Dunk was part of Brighton’s youth system before his first-team debut in 2010 and has made nearly 300 club appearances, including 110 in the Premier League.
Lewis Dunk has been capped once by England, featuring in a 3-0 friendly victory over the United States at Wembley in November 2018.
“I’m delighted to have signed a new contract,” said Dunk, whose new deal keeps him with the Seagulls until the summer of 2025.
“The aim now is to help the club continue its recent progress over the next five years.”