The 22-year-old was successful in his campaign for the government to allow 1.3 million children to claim free school meal vouchers over the summer holidays.
It is the highest honour the university can bestow.
England forward Rashford said it was “a proud day for myself and my family”.
United legends Sir Alex Ferguson and Sir Bobby Charlton have previously received the award from the university.
Rashford said: “When you look at the great names that have been awarded this doctorate in the past, it’s humbling.
“We still have a long way to go in the fight to combat child poverty in this country but receiving recognition from your city means we are heading in the right direction and that means a lot.”
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