Romelu Lukaku scored an 82nd-minute penalty as Inter Milan put themselves in a strong position to advance to the semi-finals of the Champions League after securing a deserved win away at Benfica.
In a tightly contested tie, Nicolo Barella’s downward header stunned the Portuguese league leaders and gave Inter a priceless advantage.
Benfica struggled to dictate play in front of their own fans as Inter produced a defensive masterclass in Lisbon.
Rafa Silva was denied by Andre Onana’s first-half save before Inter’s Netherlands defender Denzel Dumfries produced a crucial block from close range as Benfica pushed for an equaliser.
The Italian visitors wrapped up a solid win when substitute Lukaku, on loan from Chelsea, scored from the spot after former Inter player Joao Mario handled inside the box.
Premier League referee Michael Oliver awarded the penalty after watching a replay of the incident on the pitchside monitor, with replays showing the ball struck the side of Mario’s head before hitting his hand.
Simone Inzaghi’s side will fancy their chances of finishing the job in front of their own fans in the return leg on 19 April (20:00 BST).
Inter arrived in Portugal’s capital on the back of a poor run of form after failing to win any of their past six games.
But they took advantage of a hesitant Benfica to take a firm grip of the tie.
Barella’s decisive goal came after an excellent cross by Alessandro Bastoni, with the Italy midfielder heading it back across the keeper and into the net.
It was Inter’s first attempt on target but Benfica keeper Odisseas Vlachodimos prevented further damage by saving from former Manchester United and Arsenal player Henrikh Mkhitaryan.
This was Benfica’s 13th European game of the season after starting their Champions League campaign at the third qualifying round stage back in August.
But they did not create enough and face a mammoth task to turn the tie around after Lukaku wrapped up the victory.
The Belgium forward had missed out on a starting place to 37-year-old Edin Dzeko but made an impact from the spot after beating the keeper for pace and power.
There was still time for Benfica to reduce the deficit but Goncalo Ramos’ 89th-minute attempt was kept out by Onana on a memorable night for Inter.