An extraordinary batting collapse saw Brisbane Heat crash to a 44-run defeat against Melbourne Renegades in the Big Bash League.

Chasing 165 to win at the Gabba, the Heat made a flying start and were 84-0 in the sixth over, taking full advantage of the powerplay.

However, a batting slump of bewildering proportions saw them lose 10 wickets for 36 runs to be all out for 120, with leg-spinner Cameron Boyce taking 4-15 in his four overs.

It was the worst 10-wicket collapse in Big Bash history, league officials said.

The Heat middle and lower order owed an apology to openers Sam Heazlett and Chris Lynn, who showed sizzling form. Heazlett made 56 from 37 balls, and captain Lynn was destructive as he rattled to 41 from 15 deliveries.

Marcus Harris took a fine catch on the run, just in from the ropes, to remove Lynn, who had struck three sixes in his whirlwind knock.

Brisbane still looked set to win with several overs to spare, but an hour of largely self-inflicted carnage was just getting under way.

AB de Villiers was bowled two balls later, charmed out by a fine leg break from Boyce, and when the same bowler had Matt Renshaw caught at slip from the next ball, it was the first real sign that something was stirring.

The Heat rebuilt and at 113-3, with Heazlett and Joe Burns at the crease, they looked to have seen off the storm.

It was at that point a tempest swept in, Samit Patel removing Heazlett and Jimmy Peirson with consecutive deliveries in the 13th over. Burns was run out two balls later, sent back by batting partner Ben Cutting and falling way short of his ground.

Cutting and Josh Lalor fell in the space of three balls to Dan Christian, before Boyce stepped in to complete the onslaught. Seven wickets fell for seven runs in the wild finale.

The Renegades have put up an awful title defence, losing nine in a row until finally registering a victory in their last match when scoring a Duckworth-Lewis-Stern success against the Sydney Thunder.

This was a second victory of their lamentable season, and one to savour.

Boyce said on BT Sport: "I think we were all a bit nervous after the start. That was pretty clean striking there [by Lynn and Heazlett], so it obviously needed something pretty special.

"But after the powerplay I thought we bowled pretty well as a unit. Our season hasn't gone the way we wanted it to, but we do feel we've been close in about six or seven of our games.

"It's just been one of those years. I said last week it would be nice to repay our fans a little bit.

"We've got to take a lot of momentum and confidence out of the game. They got away in those first six but we pegged them back really nicely. Hopefully we can finish the season with a couple of wins."

The Renegades earlier reached a competitive total when Mohammad Nabi and Patel lifted them from 131-6 after the 18th over to 164-6 at the end of their innings.

Beau Webster made 36 and Shaun Marsh 27, but it was Nabi's quickfire 22 and Patel's 23 from 10 balls that put pressure on Brisbane, although nobody could have envisaged the drama to come.