Martial, 21, has started just one game in the Premier League this season under Jose Mourinho.
And Wenger reckons the French winger is a perfect replacement when Alexis Sanchez leaves Emirates.
United put down £36million to buy Martial from Monaco but there are add-ons that will see the fee rise.
According to the Sun, Arsenal may need to break the £50million barrier to land him but Wenger is willing to invest in the right player.
The Gunners boss is keeping a close eye on Martial’s situation at Old Trafford and will weigh up a move if he looks unsettled, given he has already lost his place in the France squad.