And, roared on in typical fashion by the fervent sea of red, they finished in style as Alex Corbisiero, George North, Jamie Roberts and Jonathan Sexton crossed over for a thumping win.
Corbisiero returned to the starting XV in place of England teammate Mako Vunipola and it proved to be a masterstroke.
Australian scrum-half Will Genia - a shining light for the hosts so far in the series - fumbled Sexton's kick-off, silencing the home crowd.
Skipper Alun Wyn Jones got his hands on the ball following the resulting scrum and when he was stopped short Corbisiero was on hand to pile over inside 90 seconds, much to the delight of the rapturous travelling support.
Many of the 83,702 in attendance watched on in disbelief as the Lions overpowered their hosts and Leigh Halfpenny gratefully accepted four first-half penalties.
James O'Connor's try on the stroke of half time did reduce the deficit, but not before the Israel Folau was forced off through injury, and a second-half masterclass from the rampant Lions completed the job.
Sexton was first to cross over after the break, while North added his second of the series and Roberts broke clear to rub salt into Australian wounds, wrapping up a memorable triumph for the Lions faithful.
The Lions fans fill Sydney for the decisive Test