The 45-year-old spent 11 seasons at Old Trafford, famously scoring the winning goal in the 1999 Champions League final against Bayern Munich.
He told the club’s official website: “Manchester United is in my heart and it’s brilliant to be coming back in this role. I’m really looking forward to working with the very talented squad we have, the staff and everyone at the club.”
United fired Mourinho with the club languishing in sixth place in the English Premier League, 19 points behind leaders Liverpool after Sunday’s insipid 3-1 defeat at Anfield.
Solskjaer, who recently signed a new deal as manager of Norwegian club Molde, will take charge of his first match on Saturday, against Cardiff City — a club he previously managed without much success.
Mike Phelan, a coach at United during Alex Ferguson’s managerial reign, returns to the club as assistant manager.
In a statement, United’s chief executive Ed Woodward said: “Ole is a club legend with huge experience, both on the pitch and in coaching roles.
“His history at Manchester United means he lives and breathes the culture here and everyone at the club is delighted to have him and Mike Phelan back. We are confident they will unite the players and the fans as we head into the second half of the season.”
More to follow.