Chelsea thrashed Reading 5-0 on the final day of the FA Women's Super League to be crowned champions after an excellent season in which they lost only once, with Manchester City finishing second and Bristol City relegated.
Knowing a win would secure the title for the second season in a row, Chelsea's Melanie Leupolz got the party started by scoring from a clever corner in the second minute, and Kirby combined with Sam Kerr to strike just before halftime.
The Kerr-Kirby pairing struck again 12 minutes into the second half as the Australian teed up Kirby to take a touch and lash a powerful shot past Reading goalkeeper Grace Moloney.
Kirby returned the favour in the 71st minute, lofting a pass for Kerr to volley home her 21st league goal of the season to secure the Golden Boot award.
Substitute Erin Cuthbert bundled home a fifth to make it a bittersweet end for Reading's Fara Williams, who was playing the final game of a storied career that began at Chelsea and spanned two decades in which she became England's most-capped player.
The final whistle sparked celebrations from the Blues, who have already won the Community Shield and the Continental Cup this season and face Barcelona in the Champions League final in Gothenburg, Sweden next week.
Chelsea finished the 22-game season on 57 points, two ahead of Manchester City, who beat West Ham United 1-0.
Arsenal, with Republic of Ireland's Katie McCabe starting at left-back, bagged the final Champions League qualification spot in third place on 48 points, one ahead of Manchester United.
There were sighs of relief for Aston Villa, who drew 0-0 with Arsenal, and Birmingham City, who lost 1-0 to Tottenham Hotspur, as Bristol City were the one team relegated to the Championship following a 3-1 defeat by Brighton & Hove Albion.
Ireland duo Rianna Jarrett and Megan Connolly were part of the matchday squad for Brighton but were not brought on.