The 27-year-old has made 188 league appearances for the Seagulls.
March, 27, has made 188 league appearances for the Premier League side since signing from Lewes in December 2011.
The winger has also represented his country, winning three caps for England Under-21s.
Head coach Graham Potter said: “I am really pleased to see Solly commit his future here, he is a pleasure to work with and it’s great to see him continue to progress.
“As a local lad he is a great role model and excellent example for any young player with his commitment and hard work.
“He’s a player who makes a significant impact for us at both ends of the pitch, and we are delighted he’s committed his long-term future to the club.”