The forward was among a raft of players, which included Antonio Valencia and Ander Herrera, as well as former St Johnstone and St Mirren midfielder Matty Willock, on the club's confirmed released list.
Last month it was reported that Derek McInnes wants to sign the 23-year-old on a permanent basis.
Wilson featured 33 times for the Dons during the 2018/2019 campaign , scoring four times.
It was speculated that he was on £30,000-per-week at United having broke into the first-team as a precocious youngster.
The club had high hopes for the striker but he lost his way on a number of loan spells.
However, only 12 months ago Manchester United academy coach Clayton Blackmore said Wilson is "better than Jamie Vardy" and that he was the best youngster he had seen.
Aberdeen have already signed Curtis Main, Ash Taylor and Ryan Hedges this summer.