Young took over as United skipper in the summer after Antonio Valencia departed the club, but the England international has been in and out of the side, making just 18 appearances in all competitions.
Young is expected to join Inter Milan after United agreed a £1.2m deal with the Italian side.
Maguire has already been skippering United on occasions this season when Young was absent, despite only joining from Leicester City for a record £80m in the summer.
But Old Trafford boss Ole Gunnar Solskjaer has been impressed with Maguire’s leadership qualities and has decided to hand him the role full time.
Speaking in his press conference on Friday morning, Solskjaer said: 'Harry is wearing the captain's armband and will keep wearing it. He's been a leader in the group, I've been impressed by his leadership skills, so he will continue wearing the armband.
'He's come in and everything about him tells me he's a leader, he's part of a group we've had that have been leading this young group, David (de Gea), Marcus (Rashford), Harry, so Harry will keep on wearing the armband.'
The move to make Maguire captain completes a stunning turnaround for the 26-year-old who suffered relegation from the Premier League with Hull City at the end of the 2016/2017 season.
Maguire has made 29 appearances in all competitions for Manchester United this season.