The midfielder - once seen as the leading prospect in United’s academy - revealed today that he was quitting the club, six months before the end of his deal.
Dawson, whose recent years at Elland Road have been badly affected by injury, has agreed to terminate his contract after failing to make a serious first-team breakthrough.
He came to prominence during the 2012-13 season, breaking into Wales’ Under-21 squad and making his debut in a 2-1 defeat to Derby County, Neil Warnock’s last game as manager.
He played three times under Neil Redfearn last term, featuring as a substitute in Championship games against Cardiff City, Fulham and Charlton Athletic.
In a post on Twitter, Dawson said: “Today my 15 years at LUFC has come to an end.
“So many great memories to take away with me and would like to thank all the staff who have helped me progress throughout my time here.
“Also couldn’t ask for a better group of lads to have played with and I wish them all the best for the future.”