The Red Devils confirmed the Portuguese superstar’s sensational return after striking an agreement with Juventus to pay €15m (£12.9m) plus a further €8m (£6.9m) in add-ons.
Ronaldo rejoins the club 12 years after his departure, when he joined Real Madrid in 2009 for £80m.
It also ends a three-year spell for the 36-year-old in Turin, which saw him score 101 goals in 134 matches.
Rashford tweeted: “Wow wow wow, he’s home,” adding a series of emojis while tagging Ronaldo.
With Sancho adding: “SCARY HOURS!”
A club statement read: “Manchester United is delighted to confirm that the club has reached agreement with Juventus for the transfer of Cristiano Ronaldo, subject to agreement of personal terms, visa and medical.”
While former United defender and Sky Sports pundit Gary Neville reacted to the news: “He’ll play regularly, he’ll play as a No 9, he’ll play as a centre-forward. I’m sure they’ll put legs around him. He will score goals.
“Cristiano Ronaldo will be coming to win trophies, win personal accolades. Set the Premier League on fire, it is a different Cristiano Ronaldo.
“He is a No 9, he still has bursts of speed, he makes great runs inside the box. He has anticipation of where the ball is going to drop. What he gives to Manchester United, he gives them something they need.
“To get above Manchester City, Liverpool and Chelsea, they have to do something big, this could give them a temporary shot in the arm to get them right up there this year.
“I was a bit fearful that they could improve but finish in a lesser position in the league.
“But this news gives me more hope that Manchester United can have a great season.
“What it does give every Manchester United fan is a great feeling, this is one of the most special players that has ever lived. Forget Manchester United, this is one of the greats of all time.”