Glasgow City wasted no time in making a flying start to the defence of their 14th consecutive Scottish title with a convincing 6-0 defeat of Motherwell.
Priscilla Chinchilla scored within 18 seconds for the home side, with Ode Fulutudilu finding the net twice.
Runners-up Celtic beat SWPL2 champions Aberdeen 4-2, with Charlie Wellings and Chloe Craig scoring twice each.
Hibernian defeated Spartans 3-0, while promoted Hamilton Academical edged Hearts 2-1 with a stoppage-time goal.
It was a tale of three penalties for Accies after Hearts goalkeeper Charlotte Parker-Smith saved German striker Josi Giard's spot kick before forward Aimee Anderson opened the scoring for the Edinburgh hosts with 17 minutes remaining.
But midfielder Hannah Scott equalised with Accies' second penalty minutes later before following up to secure the three points after Parker-Smith saved her second spot kick of the match.
It also took a stoppage-time penalty for Celtic to finally subdue promoted Aberdeen.
The hosts appeared to be in for a tough afternoon when striker Wellings, Celtic's summer signing from Bristol City, opened scoring after 14 minutes.
However, the Dons were level within eight minutes when defender Kelly Clarke headed a Jenna Penman cross into her own net.
Defender Craig restored the lead within another two minutes and Wellings looked to have secured the points with her own second 10 minutes from the end.
However, midfielder Eilidh Shore ensured a nervous finish for the visitors with Aberdeen's second before Craig secured the win with that late spot kick.
At Petershill, City all but secured the three points within the first six minutes thanks to goals from Costa Rica midfielder Chinchilla and Republic of Ireland centre-half Claire Walsh, their summer arrival from Peamount United.
South Africa international Fulutudilu added two more before half-time, with fellow forward Taylor Fisher and Israel midfielder Vital Kats, another summer signing, completing the scoring after the break.
Two summer arrivals helped Hibs ease to victory in their derby with Spartans.
American striker Alexa Coyle, previously of University of Montana, set them on their way with a fifth-minute penalty, defender Colette Cavanagh added the second before the break and Michaela McAlonie, their midfield signing from the visitors, scoring the third against her former team-mates.
The other SWPL1 opening game between Rangers, who were third last season, and promoted Partick Thistle was postponed because of a Covid-19 outbreak at the Firhill club.