Alexandre Lacazette scored the only goal of the game as Arsenal booked their place in the Europa League semi-finals with a clinical 1-0 win at Napoli.
Leading 2-0 from the first leg, Unai Emery's side reserved arguably their best performance of the season for their potentially daunting trip to the San Paolo.
Lacazette fired home a 25-yard free-kick in the 36th minute and, although Arkadiusz Milik had earlier had a goal ruled out for offside, the Gunners seldom looked troubled.
They will face Valencia, one of Emery's former sides, in the last four after they wrapped up victory in their all-Spanish clash with Villarreal.
Leading 3-1 from the away leg, Valencia like the Gunners were always in command as goals from Toni Lato and Daniel Parejo gave them a 5-1 aggregate victory.
Chelsea held off a second half fightback from Slavia Prague to beat the Czech side 4-3 at Stamford Bridge and move into the last four with a 5-3 aggregate win.
Maurizio Sarri's men looked set for a comfortable night when Pedro and an own goal from Simon Deli extended their advantage in the opening 10 minutes.
Olivier Giroud made it 3-0 on the night in the 17th minute and, when Tomas Soucek struck an apparent consolation, Pedro immediately replied with his second of the night.
But, roared on by the visiting supporters, Slavia staged a stirring second-half revival and two goals from Petr Sevcik gave them brief hope of a remarkable comeback.
Eintracht Frankfurt hit back from a two-goal first-leg deficit to sink Benfica on away goals and book a semi-final clash against the Blues.
The Bundesliga side began the night trailing 4-2, but dominated the first period and reduced the aggregate deficit when Filip Kostic struck a controversial opener after 36 minutes.
Benfica were convinced Kostic had been offside in the build-up to the goal and their coach Bruno Lage was sent to the stands for protesting.
Sebastian Rode wiped out the deficit in the 67th minute when he drove a powerful shot past Benfica goalkeeper Odisseas Vlachodimos from the edge of the box.
Frankfurt keeper Kevin Trapp produced a brilliant fingertip save to deny Salvio in the 79th minute as Frankfurt held on for a 4-4 aggregate draw which sent them through on away goals.
When are the Europa League semi-finals?
First legs:
- Arsenal vs Valencia, Thursday 2 May, 8pm
- Eintracht Frankfurt vs Chelsea, Thursday 2 May, 8pm
Second legs:
- Valencia vs Arsenal, Thursday 9 May, 8pm
- Chelsea vs Eintracht Frankfurt, Thursday 9 May, 8pm
