The UEL has been a welcome distraction for a Forest side firmly in the grip of a Premier League (PL) relegation battle, and the chance to create history here was not lost on a buoyant City Ground crowd.
After an early chance for Terem Moffi, momentum soon swayed in the hosts’ favour when Jan Bednarek was shown a straight red card for a high left-footed challenge on Chris Wood.
That one-man advantage soon turned into a one-goal advantage, as Morgan Gibbs-White’s effort took a hefty deflection off Pablo Rosario and flew past Diogo Costa.
Vítor Pereira’s side were playing with confidence and could have doubled their advantage had Nicolas Domínguez not dragged his shot wide.
However, not everything was going to plan, with Wood forced off with injury after feeling the ill-effects of Bednarek’s challenge.
His replacement - Igor Jesus - looked lively after entering the fray, and he headed over from Neco Williams’ corner, before Domínguez sent a glancing header wide from Dan Ndoye’s cross in first-half stoppage time.
The Tricky Trees were almost made to pay for their first-half profligacy, as William Gomes rattled the crossbar from deep inside the box after latching onto Seko Fofana’s lofted delivery.
Forest’s lead was still looking threadbare, and Pereira was forced into two more changes, taking off injured duo Callum Hudson-Odoi and Murillo.
The hosts were not playing with the same intensity, but Costa was called into action to parry away Jesus’s angled strike.
Alan Varela shredded the hosts’ nerves further when his speculative attempt cannoned off the bar, but Francesco Farioli’s side couldn’t find the breakthrough on a frustrating night for the visitors.
Ultimately, Forest had done enough to secure a European semi-final berth for the first time since overcoming Sturm Graz in the 1983/84 UEFA Cup quarter-finals.
A tantalising all-PL last-four clash with Aston Villa awaits, while Porto bow out having still yet to beat a PL team in England after 24 attempts (D3, L21).
Flashscore Man of the Match: Morgan Gibbs-White (Nottingham Forest)