Trezeguet scored a dramatic 93rd-minute winner to see off Leicester City 2-1 and send Aston Villa to the Carabao Cup final at Wembley.
The Egypt international stepped off the bench and converted an injury-time cross from compatriot, and fellow second-half substitute, Ahmed Elmohamady to send Villa Park into raptures and seal a dramatic 3-2 aggregate victory as the club secured a spot in their first major cup final since 2015.
It will be a third successive Wembley visit in as many seasons, where Dean Smith's side will face either Manchester City or Manchester United on Sunday, March 1.
Villa, inaugural winners of the competition in 1961, will be bidding to win the League Cup for the sixth time having reached the final on a ninth occasion.
Following a 1-1 draw in the first leg, Matt Targett put the hosts ahead on the night in the 12th minute only for Kelechi Iheanacho to level in the second half and seemingly send the semi-final to penalties before Trezeguet's late winner.
Villa were indebted to a superb display from goalkeeper Ørjan Nyland, who made a series of superb first-half saves to keep out the Foxes.
Dean Smith handed a debut to new signing Mbwana Samatta in attack as part of three changes from the last-gasp win over Watford, with Douglas Luiz and Nyland also returning.
And, amid a pulsating start to proceedings, it was the Norwegian who was twice called into action inside the opening nine minutes to get down low and superbly deny James Maddison.
Those saves proved crucial as Villa opened the scoring just moments later. Frederic Guilbert won possession in the middle of the park and found Luiz, who fed Jack Grealish inside the penalty area and he laid the ball outside for Targett to smash home.
Nyland again came to the rescue shortly after the half-hour mark when he produced a brilliant one-handed save to push Youri Tielemans’ strike on to the crossbar, preserving the half-time advantage.
Samatta came close to doubling the lead in the 65th minute but he narrowly failed to connect with Grealish's teasing cross.
Keinan Davis made his return from injury shortly afterwards, replacing the Tanzania international.
Yet it was the Foxes who levelled matters in the 72nd minute, Iheanacho arriving at the back post to slot home Harvey Barnes' low ball across the six-yard box.
With both sides looking for a late winner, Maddison fired over for the visitors when well placed, Kasper Schmeichel denied Trezeguet at the other end before Jonny Evans headed narrowly off target.
However, Trezeguet had the final say in the semi-final when he converted Elmohamady's deep cross from close range, ensuring Villa secured a second successive injury-time victory in the space of a week.
Villa: Nyland, Konsa, Mings, Hause, Guilbert (Elmohamady 84), Luiz, Nakamba, Targett, El Ghazi (Trezeguet 77), Samatta (Davis 67), Grealish.
Subs: Sarkic, Chester, Lansbury, Hourihane.
Goals: Targett (12), Iheanacho (72), Trezeguet (90+3)
Villa return to Premier League action on Saturday with a trip to the south coast to face Bournemouth (ko 3pm).