After taking part in his first training session at Carrington, he revealed hes relishing a new challenge for silverware with the Reds, for whom he'll wear shirt no.20.
The 29-year-old told a press conference on Friday: "I'm proud to be here and looking forward to achieving big things with Manchester United.
"Arsenal are a big club but for me it's a big challenge to get to know players here.
"I had a good session this morning I noticed every single person was really helpful. It's a friendly club like I'm used to, so it's not a big difference. The language is the same."
He continued: "Everyone knows by now that I'm a lover of football. I'm quite principled in that respect. It's always difficult to find a perfect match but I do feel this is the perfect match for me.
"Manchester United breathe football. If you look at all players at the club, the stadium and the manager, my choice was made based on those things. When I have to make hard decisions, I always listen to little boy inside me and what he wants. That little boy was screaming for United."
Arsenal fans are certain to be disappointed to see van Persie leave, but the 2011/12 Premier League top scorer was keen to ensure he left the Emirates