McTominay's international future had been the subject of much speculation, but the 21-year-old ultimately snubbed interest from England to pledge his allegiance to Scotland.
McTominay, who qualifies for Scotland through his grandparents, has cemented a position in United's first XI in recent weeks with a series of impressive performances.
Goalkeepers: Jordan Archer (Millwall), Alan McGregor (Hull City), Jon McLaughlin (Heart of Midlothian)
Defenders: Barry Douglas (Wolverhampton Wanderers), Grant Hanley (Norwich City), Russell Martin (Rangers), Scott McKenna (Aberdeen), Charlie Mulgrew (Blackburn Rovers), Callum Paterson (Cardiff City), Andy Robertson (Liverpool), Kieran Tierney (Celtic)
Midfielders: Stuart Armstrong (Celtic), Tom Cairney (Fulham), James Forrest (Celtic), Ryan Fraser (Aberdeen), Kevin McDonald (Fulham), Dylan McGeouch (Hibernian), John McGinn (Hibernian), Calum McGregor (Celtic), Kenny McLean (Aberdeen), Scott McTominay (Manchester United), Jamie Murphy (Rangers), Matt Ritchie (Newcastle United)
Forwards: Ryan Christie (Aberdeen), Jason Cummings (Rangers), Oliver McBurnie (Barnsley), Matt Phillips (West Bromwich Albion)