After Ander Herrera had given the Spanish the lead, Welbeck popped up two minutes from time to calmly stroke the ball beyond De Gea, who is widly tipped to be United's new stopper next season.
The 20-year-old was otherwise impressive between the sticks for Spain, sprawling to his left in the first half to keep out Kyle Walker's deflected cross and beginning many of the Spaniard's free-flowing attacks.
But the headlines belong to Welbeck, whose cool finish ensures England go into their final two group games optimistic they can qualify for the semi-finals.
Welbeck said:"We created quite a few chances in the second half and we got more possession. Maybe if we stick away a few more of our chances, we can progress."