The Netherlands international moved from the Emirates Stadium to Old Trafford last year and was a major part of United's Premier League winning side last season, but Wenger believes his loyalties will always draw him to his former club.
Van Persie joined Arsenal from Feyenoord in 2004 and went on to become the club's eighth highest scorer with 132 goals.
He will face Arsenal for the third time since leaving on Sunday, and Wenger admitted he still finds it odd seeing the 30-year-old in the red of United and not his side.
"Of course it's strange because for me he is an Arsenal man," the Frenchman said.
"I took him when he was a very, very young player.
"We have gone together through very difficult periods and he became a world-class player and for me he is an Arsenal player."
Van Persie has scored nine goals in 13 appearances for United this season, adding to the 30 he scored in all competitions last term.
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