Protecting a slender 1-0 lead after last week's quarter-final first leg, the A-League side did just enough against the defending champions to advance on away goals in dramatic circumstances on Wednesday.
Tomi Juric scored the crucial away goal from the penalty spot to give the Wanderers a shock lead 14 minutes after the break, but goalkeeper Ante Covic was the real hero.
Covic saved a first-half spot-kick from Elkeson and kept out almost everything the star-studded Guangzhou attack threw at him.
Alessandro Diamanti's strike just after the hour mark gave the home side hope of a fightback before Elkeson set-up a grandstand finish with a goal in stoppage time.
But the Wanderers were not to be denied a famous result that sets up a semi-final clash with Korean giants FC Seoul.
Alberto Gilardino was denied by the woodwork as the home side started well and their early pressure was rewarded when Iacopo La Rocca clumsily brought down Elkeson to concede a penalty.
The Brazilian, however, blasted his spot-kick attempt down the middle, with Covic showing all his experience to stay big and parry it away.
Tony Popovic's side were holding on, but a rare foray forward 13 minutes after the break saw them grab the vital away goal.
Mark Bridge found himself one-on-one with Zeng Cheng and, despite getting a shot in, was brought down by the goalkeeper for a penalty, which was coolly converted by Juric to silence the home fans.
It meant Guangzhou needed to score three times to advance and they managed to get one back just two minutes later.
It was the Italians who combined with Gilardino nodding down for Diamanti to blast it under Covic with a powerful strike from just inside the box.
Gilardino, Elkeson and Dong Xuesheng all missed glorious chances in the latter stages before the Brazilian pulled another one back in stoppage time. But the Wanderers held on to become just the second Australian club after Adelaide United in 2008 to make the ACL semi-finals on what was a momentous night for the club.
