A stunning unbeaten century by South African powerhouse Lizelle Lee has propelled the Melbourne Stars to an upset victory over the Sydney Sixers in the opening round of the WBBL.

Lee plundered 102 off 56 balls to lead the Stars, chasing a target of 166, to a seven-wicket win over the defending champions at Melbourne's Junction Oval on Saturday.

It's the equal fourth-highest score in WBBL history and highest by a Stars player.

Big-hitting opener Lee capped off a sensational knock by bringing up her century with a six over long on - her third of the innings to go along with 16 fours - before scoring the winning runs.

It was a welcome change of fortunes for Lee, who twice missed opportunities to dismiss Sixers captain Alyssa Healy - first fumbling a stumping opportunity then dropping a simple chance directly behind the stumps with Healy on 35.

Lee also benefited from some sloppy fielding, gaining a lifeline on 90 when Sara McGlashan dropped an absolute sitter at mid-off.

Few had given the Stars much chance against the competition favourite Sixers, who are chasing their third straight title.

"There's nothing wrong with being the underdogs," Lee said.

"We're really a good team compared to last year ... a few youngsters look really good and also the bowlers have done extremely well today."

Australia's World Cup hero Healy picked up where she left off in the Caribbean, scoring a poised 70 off 47 balls to gift the Sixers a dream start.

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Days after guiding Australia to their fourth T20 World Cup triumph, player of the tournament Healy and star allrounder Ellyse Perry (58) showed no signs of fatigue.

Fast bowler Nicola Hancock (4-22) lit a much-needed spark for the Stars, bowling Perry before ripping through the Sixers' middle order to restrict them to 7-165.

"Given the start we had, we probably (finished) 15 or 20 runs short which maybe wouldn't have been enough anyway in the end," Perry said.

"We certainly left some runs out there in really great conditions ... we were just outdone today."