Marc Skinner's Adobe FA Cup finalists will meet the Blues on Sunday 4 May, with the special occasion kicking off at 12:00 BST.
Tickets are still available for the contest, a repeat of the semi-final clash at the weekend, which we won 2-0, courtesy of goals from Celin Bizet and Grace Clinton, at the Joie Stadium.
United are currently third in the WSL table, level on points with second-placed Arsenal and six adrift of leaders Chelsea.
With the Champions League push very much on for Skinner's side, this is a key fixture against City, who are currently in fourth, with a gap of seven points between the two Manchester clubs.