The Premier League pair are the two favourites to lift the trophy on May 21 in Bilbao and can now map out their routes to the final, where they will meet each other should they both get there.
Athletic Bilbao will also fancy their chances, especially with the final being held at their home stadium, and face Roma in the last-16 stage. Lazio, considered the fourth-favourites, must get past FCSB to reach the quarter-finals.
Rangers have been handed a tricky test against Fenerbahce.
The first legs in the last 16 will be played on March 6, with the return fixtures a week later.
Europa League last-16 draw in full
Eintracht Frankfurt vs Ajax
Manchester United vs Real Sociedad