Dirk Kuyt struck the extra-time winner which will be worth millions to Liverpool as they secured their place in the Champions League group stages.
Kuyt has been Liverpool's lucky charm in such games, and this was his ninth goal in 15 European outings.
Last season he scored seven times as Liverpool reached the semi-finals, but none were worth more than the one he forced over the line tonight with two minutes of extra-time left.
Liverpool had stood on the brink of a shattering elimination from the competition as brave Liege pushed them to the very limits.
But somehow Liverpool held their nerve, winning through after another performance which left much to be desired.
Brazilian full-back Fabio Aurelio replaced new signing Andrea Dossena for Liverpool, the only change from the side that beat Middlesbrough on Saturday.
Such was the impact Liege made on Liverpool in the first leg, maybe that change was a reflection on the hounding Dossena suffered from Wilfried Dalmat a fortnight ago.
The Belgian champions, trying to reach the group stages for the first time, had American defender Oguchi Onyewu back from suspension and he came into coach Laszlo Boloni's side.
Roared on by 3,000 noisy Belgians, Liege went searching for the away goal which they knew would make Liverpool's task so much more difficult.
It took a fine, low save from Jose Reina after seven minutes from Dieumerci Mbokani's 20-yard shot to keep Standard from taking that early lead.
Liverpool responded with an Aurelio curling free-kick which was punched away by Aragon Espinoza, with Fernando Torres and Robbie Keane both failing to capitalise on the loose ball.
Then Steven Gerrard's instant pass into Yossi Benayoun's feet ended with the little midfielder mis-hitting his shot wide.
But Liege were intent on testing Liverpool. Marouane Fellaini forced Reina into another save, stretching full-length to his right, Mbokani having failed to connect seconds earlier as the ball dropped invitingly in the box.
In a very open game, Xabi Alonso saw a 25-yard strike skim away from goal with Espinoza beaten.
Liege were certainly not overawed by Anfield, and their pace and confidence increased by the minute.
They had run Liverpool ragged in the first game, and at times they achieved the same effect in this second match.
Fellaini and Steven Defour were again giving Liverpool plenty to worry them in midfield, picking up possession and breaking Liverpool's flow.
Another Aurelio effort saw Espinoza in action again, but Liverpool were not making genuine chances.
The talented Mbokani, with four goals already this season, was engaged in an uncompromising war with Martin Skrtel while Dalmat and Axel Witsel on the flanks stretched Alvaro Arbeloa and Aurelio.
Liverpool opportunities were rare. Kuyt, in his 100th game for the club, headed wide from Aurelio's corner after 40 minutes, but the game was not going according to the home side's script.
Belief was flooding through Liege's minds and bodies, and Liverpool were not playing well and making too many unforced errors.
Defour volleyed over the bar, and there was pressure and tension every time Liege got near Liverpool's area.
The longer it went on, the more mistakes were made. Alonso's passing often went astray, with Benayoun seemingly unable to find a red shirt while Keane was virtually anonymous.
Mohamed Sarr was booked after an hour for a foul on Torres, with Ryan Babel replacing Benayoun before the re-start.
Torres then worked his way through to see a shot blocked by Onyewu, who was having a fine game in defence to keep the Spaniard relatively quiet.
Alonso produced a rare shot after a quick-passing move, but Espinoza was equal to it.
Liverpool continued to labour, with Keane missing in the area after being set-up by Kuyt.
Gerrard fired over the bar soon afterward, and then saw an angled cross-shot fly well wide.
With seven minutes of the regulation 90 left, Benitez sent on youngster Nabil El Zhar for Keane, with Kuyt pushing forward to support Torres.
Igor De Camargo headed just wide in the closing minutes, Milan Jovanovic having replaced Dalmat, but extra-time was an inevitability.
The tension escalated, and Liverpool upset the Belgians by not returning the ball after it had been kicked out for a player to have treatment.
Then Bonfim Dante was booked for a foul on El Zhar, amid continued exchanges of views on the benches.
Liege sent on Salim Toama after 100 minutes for De Camargo, but still Liverpool were making bad errors while the visitors kept coming forward with confidence.
In the second period of extra-time, Espinoza was finally extended when he beat away a 30-yard shot from Arbeloa, with Torres heading wide soon after.
El Zhar should have had a penalty when he was sent tumbling in the box, but eventually Liverpool forced their way ahead.
Babel crossed from the left with just two minutes left, and Kuyt forced the ball home on the far post for the only goal of the tie, leaving Liege barely any time to regroup.
Kuyt has been Liverpool's lucky charm in such games, and this was his ninth goal in 15 European outings.
Last season he scored seven times as Liverpool reached the semi-finals, but none were worth more than the one he forced over the line tonight with two minutes of extra-time left.
Liverpool had stood on the brink of a shattering elimination from the competition as brave Liege pushed them to the very limits.
But somehow Liverpool held their nerve, winning through after another performance which left much to be desired.
Brazilian full-back Fabio Aurelio replaced new signing Andrea Dossena for Liverpool, the only change from the side that beat Middlesbrough on Saturday.
Such was the impact Liege made on Liverpool in the first leg, maybe that change was a reflection on the hounding Dossena suffered from Wilfried Dalmat a fortnight ago.
The Belgian champions, trying to reach the group stages for the first time, had American defender Oguchi Onyewu back from suspension and he came into coach Laszlo Boloni's side.
Roared on by 3,000 noisy Belgians, Liege went searching for the away goal which they knew would make Liverpool's task so much more difficult.
It took a fine, low save from Jose Reina after seven minutes from Dieumerci Mbokani's 20-yard shot to keep Standard from taking that early lead.
Liverpool responded with an Aurelio curling free-kick which was punched away by Aragon Espinoza, with Fernando Torres and Robbie Keane both failing to capitalise on the loose ball.
Then Steven Gerrard's instant pass into Yossi Benayoun's feet ended with the little midfielder mis-hitting his shot wide.
But Liege were intent on testing Liverpool. Marouane Fellaini forced Reina into another save, stretching full-length to his right, Mbokani having failed to connect seconds earlier as the ball dropped invitingly in the box.
In a very open game, Xabi Alonso saw a 25-yard strike skim away from goal with Espinoza beaten.
Liege were certainly not overawed by Anfield, and their pace and confidence increased by the minute.
They had run Liverpool ragged in the first game, and at times they achieved the same effect in this second match.
Fellaini and Steven Defour were again giving Liverpool plenty to worry them in midfield, picking up possession and breaking Liverpool's flow.
Another Aurelio effort saw Espinoza in action again, but Liverpool were not making genuine chances.
The talented Mbokani, with four goals already this season, was engaged in an uncompromising war with Martin Skrtel while Dalmat and Axel Witsel on the flanks stretched Alvaro Arbeloa and Aurelio.
Liverpool opportunities were rare. Kuyt, in his 100th game for the club, headed wide from Aurelio's corner after 40 minutes, but the game was not going according to the home side's script.
Belief was flooding through Liege's minds and bodies, and Liverpool were not playing well and making too many unforced errors.
Defour volleyed over the bar, and there was pressure and tension every time Liege got near Liverpool's area.
The longer it went on, the more mistakes were made. Alonso's passing often went astray, with Benayoun seemingly unable to find a red shirt while Keane was virtually anonymous.
Mohamed Sarr was booked after an hour for a foul on Torres, with Ryan Babel replacing Benayoun before the re-start.
Torres then worked his way through to see a shot blocked by Onyewu, who was having a fine game in defence to keep the Spaniard relatively quiet.
Alonso produced a rare shot after a quick-passing move, but Espinoza was equal to it.
Liverpool continued to labour, with Keane missing in the area after being set-up by Kuyt.
Gerrard fired over the bar soon afterward, and then saw an angled cross-shot fly well wide.
With seven minutes of the regulation 90 left, Benitez sent on youngster Nabil El Zhar for Keane, with Kuyt pushing forward to support Torres.
Igor De Camargo headed just wide in the closing minutes, Milan Jovanovic having replaced Dalmat, but extra-time was an inevitability.
The tension escalated, and Liverpool upset the Belgians by not returning the ball after it had been kicked out for a player to have treatment.
Then Bonfim Dante was booked for a foul on El Zhar, amid continued exchanges of views on the benches.
Liege sent on Salim Toama after 100 minutes for De Camargo, but still Liverpool were making bad errors while the visitors kept coming forward with confidence.
In the second period of extra-time, Espinoza was finally extended when he beat away a 30-yard shot from Arbeloa, with Torres heading wide soon after.
El Zhar should have had a penalty when he was sent tumbling in the box, but eventually Liverpool forced their way ahead.
Babel crossed from the left with just two minutes left, and Kuyt forced the ball home on the far post for the only goal of the tie, leaving Liege barely any time to regroup.
