A member of the infamous Busby Babes, Dawson also played for Preston, Bury, Brighton and Brentford in a glittering 16-year career.
A United statement read: “Our deepest sympathies are with the loved ones of former United forward and Busby Babe, Alex Dawson, who has sadly passed away at the age of 80. He will be fondly remembered by all of us at the club. May he rest in peace.”
Dawson, a trainee under Matt Busby in the mid-1950s, scored on his debut for the Old Trafford club as a 17-year-old in a 2-0 win over Burnley in 1957.
He featured more regularly after the Munich air disaster the following year, when 23 people lost their lives, 11 of whom were either United players or staff.
Dawson netted in the club’s first game after the crash, a 3-0 home win over Sheffield Wednesday in the FA Cup.
He joined Preston in 1961, scoring more than 100 goals for the Lilywhites – including one in the 3-2 FA Cup final loss to West Ham in 1964.
A Preston statement read: “Everyone at Preston North End is deeply saddened to learn of the passing of legendary forward Alex Dawson at the age of 80.
“Our thoughts are with Alex’s loved ones at this sad time, he will be forever in our hearts.”
Additional reporting by PA