Zlatan Ibrahimovic scored twice, as Jose Mourinho’s tenure at Old Trafford started off with a win against Southampton.
Ibrahimovic scored either side of the break, including a second half penalty, to bring his total to three goals in two league games.
French international Paul Pogba played the full 90 minutes in his return to Manchester United.
Southampton is still winless having drawn with Watford on opening day.
Manchester United: De Gea, Valencia, Bailly, Blind, Shaw, Mata (Mkhitaryan 76), Fellaini, Pgoba, Rooney (Smalling 89), Martial (Herrera 82), Ibrahimovic.
Unused subs: Romero, Schneiderlin, Young, Rashford.
Goals: Ibrahimovic (36, 52).
Southampton: Forster, Cedric, Fonte, Van Dijk, Targett, Romeu (Clasie 12), Davis (Austin 67), Hojbjerg, Tadic, Redmond, Long (Rodriguez 84).
Unused subs: McCarthy, Yoshida, Ward-Prowse, Pied.