• Mehdi Taremi hit the post and then the crossbar in injury time for Porto.
• Inter, three-time European champions, join city rivals AC Milan in Friday's quarter-final draw
Inter Milan moved into the Champions League quarter-finals for the first time since 2011 as they eliminated Porto in their last-16 tie.
The Italian side won 1-0 in the first leg at the San Siro and were able to frustrate their opponents in Portugal.
In a frantic finish, Mehdi Taremi hit the post and then the crossbar in injury time for Porto, who also had Brazilian winger Pepe sent off.
Away goalkeeper Andre Onana also made a number of key saves as Inter held on.
Porto, second in the Primeira Liga, were without 40-year-old Portugal defender Pepe, a three-time Champions League winner with Real Madrid, while midfielder Otavio was suspended after his red card for two bookable offences in the first leg.
The hosts had the best chances in the first half but Onana made a fine save to keep out Mateus Uribe's 25-yard strike.
Taremi also curled a shot wide, Evanilson saw his effort blocked by Federico Dimarco's excellent sliding challenge and Stephen Eustaquio was unable to get a touch on an inviting low cross.
Uribe fired a volley over in the second half, Onana denied Marko Grujic and Inter's Denzel Dumfries cleared a shot off the line but the home side could not make the breakthrough as Inter defended excellently.
Edin Dzeko had the visitors' best opportunity with a low, angled strike but was denied by home goalkeeper Diogo Costa.
Inter, three-time European champions, join city rivals AC Milan in Friday's quarter-final draw, which takes place at 11:00 GMT at Uefa's headquarters in Nyon, Switzerland.
Bayern Munich, Benfica, Chelsea and Manchester City are also in the last eight.
Serie A leaders Napoli, 18 points clear of Inter, could become the third Italian side through as they hold a 2-0 advantage over Eintracht Frankfurt before Wednesday's second leg, while Real Madrid lead 5-2 against Liverpool after their first-leg victory at Anfield.
Inter's last appearance in the Champions League quarter-finals came 12 years ago when they lost 7-3 on aggregate to German side Schalke.