Powell joined United from Crewe Alexandra at the start of last season but found first-team chances at Old Trafford limited, making just six appearances in all competitions.
Manager David Moyes has decided to allow the 19-year-old to leave the club temporarily in order to gain more first-team experience, and Wigan chairman Dave Whelan believes that the job they did with Tom Cleverley on loan helped them secure Powell's signature.
"We obviously had Tom Cleverley on loan and I think United were happy with the job we did with him, so it's good news that we've got the lad. We've done the deal for a season long loan," Whelan told BBC Sport.
Meanwhile, Manchester United are yet to complete a signing on deadline day although Everton midfielder Marouane Fellaini is thought to be nearing a move to Old Trafford.