Sweden great Ibrahimovic spent just less than two seasons with the Red Devils under Jose Mourinho, joining in July 2016 and departing in March 2018 to move to LA Galaxy.
During his first campaign at Old Trafford, Ibrahimovic missed out on United's UEFA Europa League final triumph against Ajax because of a serious knee injury and he will now aim to be the downfall of his former employers in this season's competition.
United has been eliminated by Milan in European knockout ties four times, the most of any side along with Real Madrid.
Arsenal, a finalist as recently as 2019, will hope there is no sense of deja vu in its tie against Olympiacos. Mikel Arteta's side suffered a shock exit against the Greek outfit at the Round of 32 stage last season.
Mourinho is out to win the competition for a second time as a coach, and his Tottenham Hotspur side faces Dinamo Zagreb, while Roma has a tricky contest against Shakhtar Donetsk, which was the last winner of the tournament in its previous guise the UEFA Cup in 2009.
Rounding out the draw, Ajax faces Young Boys, Slavia Prague goes up against Steven Gerrard's runaway Scottish Professional Football League leader Rangers, and Granada takes on Molde.
UEFA EUROPA LEAGUE ROUND OF 16 DRAW
Ajax v Young Boys
Dinamo Kiev v Villarreal
Roma v Shakhtar Donetsk
Olympiacos v Arsenal
Dinamo Zagreb v Tottenham Hotspur
Manchester United v AC Milan
Slavia Prague v Rangers
Granada v Molde