The 23-year-old's contribution has been integral to the Red Devils' campaign which sees them in the running for both the Premier League and Champions League.
Mourinho told BBC Radio Five Live: "I think the player of the year must be the best of the year but also a winner of the year. I don't think it can be a player without a big trophy.
"Clearly, what Ronaldo did this year has been magnificent and by some distance he has been the best player in the Premier League.
"For me the best is always a winner because football is a collective sport.
"So, if Manchester United does something important by winning the Premier League or Champions League I, and not just me but the whole football world, would give him the Golden Boot."