The host, comedian Celeste Barber, whose own fundraising efforts have raised $51.3 million through a Facebook campaign, launched the show with an early political dart.
"It's been such a hectic time. As Aussies, we bear together and look after each other — because it turns out the people at the top don't," she said to a big cheer from the crowd.
Barber told fans they were in for a "wicked night" with "epic" names like Olivia Newton-John and Alice Cooper, plus "multiple costume changes" by herself, she joked.
75,000 attended the concert at Sydney Olympic Park, with 23 artists performing at an event that is being broadcast nationally and to the US, UK and New Zealand.
$7,158,576 had been raised as of 8:00pm (AEST).
