Ronaldo said: "I believe we'll win the Premier League and Champions League this season.
"I'm at one of the best clubs in the world and I must think like that. If I was still playing for Sporting Lisbon I wouldn't say that but I play for Manchester United and we always have the opportunities to win the big trophies every season.
"All the players feel good, feel sharp, feel quick and they are showing on the pitch their great desire to play for Manchester United."
The Red Devils have bagged 16 goals in their last four games, with Saturday's 4-1 thrashing of Middlesbrough their eighth straight victory.
Ronaldo, 22, added: "The last three or four games, we've scored many goals and it's not just me - many players are scoring goals and this is good for our motivation. The team are more confident now. We are playing well - the last three weeks we've been fantastic and we need to keep it going."