The Portugese full back has had his contract extended until June 2028 with a one-year extension option.
The 24-year-old joined United from Porto in 2018 and has played 107 times for the club.
“As a group of players, we all feel like we are at the start of a special journey right now…everyone is intensely focused on preparations for the FA Cup final,” he said.
Dalot, who has appeared in 42 matches across all competitions this season and has made 11 senior appearances for Portugal.
He played the entire 120 minutes in United’s FA Cup semi-final triumph over Brighton on penalties after starting the League Cup final victory over Newcastle in February, which helped United win their first trophy since 2017.
After finishing third in the Premier League to qualify for the Champions League, United will take on Manchester City in the FA Cup final at Wembley on Saturday.