"Leeds United are devastated to confirm that a supporter sadly passed away ahead of our Premier League fixture with Manchester United at Elland Road, following a medical emergency in the ground before kickoff," the club said in a statement.
"The thoughts of everyone at Leeds United are with the family and friends of the supporter at this exceptionally difficult time."
Leeds drew 1-1 with United after Brenden Aaronson's opener for the home side was cancelled out by Matheus Cunha.