Benfica s Uruguayan forward Darwin Nunez (C-R) goes for a header and scores a goal against Ajax Amsterdam s Cameroonian goalkeeper Andre Onana during the UEFA Champions League round of 16 second leg football match between Ajax and Benfica at the Johan Cruijff ArenA, in Amsterdam, on March 15, 2022 (Photo: AFP)
Nunez found the net with a 77th-minute header off a free kick from the right side to help Benfica make it to the last eight for the fifth time.
The teams had drawn 2-2 in the first leg in Portugal.
Two-time European champion Benfica, which began this year's campaign in the third qualifying round, was eliminated by Bayern Munich in the 2016 quarterfinals.
Ajax was one of three teams that won all six group-stage matches, along with Liverpool and Bayern. The Dutch club was in the last 16 for the second time since 2006, though it reached the semifinals the last time it got this far three seasons ago.
Ajax had already equaled its most prolific Champions League campaign with 22 goals but struggled to capitalize on its chances in Amsterdam. Striker Sebastien Haller, the first player to score in his opening seven Champions League games and the quickest to reach 11 goals in the competition's history, had a goal disallowed for offside early in the game.
The win extended Benfica's unbeaten run in all competitions to eight games, though it was coming off a 1-1 home draw against Vizela in the Portuguese league on Friday.
In the other round-of-16 match Tuesday, Atletico Madrid advanced 2-1 on aggregate after beating Manchester United 1-0 in England.
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