Rashford will have the operation “imminently” and is expected to be out until October.
A club statement on Friday read: “Following consultation between Marcus, the manager, club medical staff and a specialists, Marcus will undergo surgery imminently to resolve his shoulder injury.
“He will now focus on his rehabilitation in order to return as soon as possible.”
Rashford played through the pain last season, carrying both shoulder and foot problems for the majority of the campaign.
After returning from holiday after the tournament, Rashford held talks with Ole Gunnar Solskjaer and club staff before deciding to have surgery.
Anthony Martial is also due back in training as he steps up his recovery from a knee injury that saw the Frenchman miss the end of last season.