Liverpool are in Rome with a 5-2 first leg advantage but Roma have already staged a second leg comeback to knock Barcelona out.
With home advantage the Italian side will be looking to hit back at the reds early, a 3-0 win for Roma would see them through to the final to face Real Madrid.
Meanwhile, the reds are playing their 10th semi-final and looking to make it to an 8th final.
For Roma, Edin Dzeko is their main man.
Strap yourselves in.
As it happened...
Sadio Mane returns to the Liverpool line-up
Liverpool: Karius, Alexander-Arnold, Lovren, Van Dijk, Robertson, Henderson, Milner, Wijnaldum, Mane, Salah, Firmino.
Subs: Mignolet, Clyne, Klavan, Moreno, Ings, Solanke, Woodburn.
Stadium already has thousands inside, and Liverpool make their way on to the pitch as part of the warm up.
Loud boos from the Roma fans but plenty of Liverpool fans are also in the stadium and Jordan Henderson acknowledges their chants.
It's going to be an atmosphere!
20 minutes until kick off.
Liverpool have been training in their black training tops, and Mo Salah entered the field to a wry smile as he looked around his former club's stadium.
Will he play a pivotal role in this tie?
Been some farcical scenes outside the ground with 5,000 Liverpool fans expected to enter via just three turnstiles.
Majority of LFC fans now inside the stadium.
Teams are out...
6' Dzeko had done well near the touchline to hold off the Liverpool defence. He sends it across the face of goal...
... but nobody there.
SADIO MANE picks up the weighted pass by Roberto Firmino and fires it in.
11' Nainggolan, linked with Man Utd this week, balloons it over the Liverpool crossbar.
15' Total mishit in the reds area and it bounces off James Milner into the Liverpool net. Lucky barstewards.
20' Roma targeting Dejan Lovren's side of central defence with all their balls in to the edge of the area.
It was his clearance that hit Milner for the own goal and now Schick gives him a slight push inside the penalty area.
25' Robertson with a steaming run down the wing - gets in the area.
Crosses to Mane and the keeper tips it wide for a corner.
26' IT'S HIS FIRST EVER LFC AWAY GOAL!
Gini Wijnaldum heads it in.
33' It's a good challenge by Alexander-Arnold on Liverpool's touchline and he manages to win the reds a goal kick off the Roma forward.
35' It's off the post for Roma. El Shaarawi shot at the edge of the box is deflected off Milner, wrong footing Karius, but it hits the post.
37' Good solid punch for Karius from a cross but he took a bit of time to get back up after it. Well done Loris.
44' That's a yellow card for Dejan Lovren for holding off El Shaarawy at the very side edge of the penalty area.
Free kick to Roma.
Pellegrini ballons his free kick
Wonderful half from the reds.
2-1 up. That's 7-3 on aggregate.
Let's get this job completed now.
46' Mo Salah flagged offside as he was bearing down on a one on one. That was a very close decision.
49' Edin Dzeko incorrectly flagged offside just seconds before he's brought down by Karius.
Let off for Liverpool.
52' Edin Dzeko grabs a goal back. Error by Alexander-Arnold allowed the winger to bypass him. Dzeko with his 8th goal of the competition.
55' Roma make a tactical change. Cengiz Under brought on for Pellegrini.
Three more goals required for Roma to force extra-time.
56' Mane with a powerful run, it finds Robertson who drills across the face of goal but Salah is a yard or two short of reaching it.
56' Free kick to Roma at the corner of the box. Alexander-Arnold adjudged to have fouled Dzeko.
Kolarov corner sent in, Dzeko gets his head to it but it goes wide for a goal kick.
60' Long ball by Roma from de Rossi, and Under is ahead of Robertson and hits it first time. Good stop from close range by Karius.
63' Ball bobbles over in the Liverpool area and El Shaarawy shoots but defender by Alexander-Arnold. It hit his hand, admittedly from about 2 yards.
66' Kolarov drills one and Karius called into action again. Moment later Dzeko beats the offside trap and puts the ball wide. Liverpool players were waiting for the flag to be raised.
70' Gonalons is on for de Rossi. Liverpool yet to make a sub although they do have players warming up on the touchline.
71' Dzeko holds up the ball and Gonalons is running in at the edge of the area and smashes it over the bar.
Roma have enjoyed a little spell there of threat but it appears to have eased a bit now.
Liverpool stroking the ball around the pitch now.
75' El Shaarawy goes off and on comes Antonucci.
80' Dejan Lovren called into action to help clear the ball.
Surely too much for Roma to do now. They are leaving even more gaps at the back now.
Reds about to make a change.
83' Klavan is on to replace the excellent Sadio Mane.
85' Liverpool fans feeling confident enough now for a rending of 'We Shall not be moved!'
86' Uh oh. Roma's Nainggolan has space at the edge of the area and he smashes it in off the post.
It's 3-2 now to Roma (5-7).
LFC Sub - Firmino off and Solanke on.
Not long to go
Penalty to Roma.
90+3 And Nainggolan scores from the spot.
4-2 to Roma.
WE'RE IN TO THE FINAL!
Got a little bit interesting in that second half but Liverpool head to Kiev to face Real Madrid.
Ends 7-6 on aggregate.
Henderson: 'Amazing effort. We knew it would be tough. Could have been more clinical. Didn't handle the last ten minutes well - we need to stop that but overall delighted to reach the final.'
Robertson: 'What a thing to be involved with. All the lads and the fans deserve it. We'll enjoy this tonight and think about (Real Madrid) later'
Wow. An eighth European Cup final for Liverpool incoming.
It's been a terrific campaign that started back in the 3rd qualifying round in August.
Next up for the reds is a game against Chelsea were they can ensure that they are definitely in this competition next season.