The Blues began the day level on 52 points with Manchester City Women at the summit but with a marginally superior goal difference, as their title rivals travelled to take on Aston Villa.
City would have needed to best Chelsea's scoreline by three goals or more to pip Hayes's team to the title, but the Blues put paid to that idea with a demolition of Marc Skinner's side at the Theatre of Dreams.
Mayra Ramirez sparked the goal rush with a well-taken header just two minutes into the match, before Johanna Rytting Kaneryd doubled the Blues' lead inside the opening 10 minutes.
Sjoeke Nusken - on as a substitute for the injured Catarina Macario - then got in on the act before Ramirez notched her second of the tie, ensuring that Chelsea would have one hand firmly on the trophy.
The fairytale ending for Hayes was sealed in style in the second half, as Melanie Leupolz struck the visitors' fifth goal before Fran Kirby - also departing Chelsea at the end of the season - completed a title-winning rout.
Hayes enjoys dream farewell as Man City fall short
In her final match of a glittering Chelsea reign, there was no wiping the beaming smile off of Hayes's face as the Blues won their fifth straight top-flight crown, taking the 47-year-old's total trophy haul to a staggering 15 as she embarks on her next adventure in North America.
While Man City did emerge triumphant at Villa Park, their 2-1 success was inconsequential, as was Arsenal's 5-0 battering of Brighton & Hove Albion, with the Gunners confirmed to finish third either way.
However, on a day of emotional goodbyes, there was a last-ever Arsenal goal for departing striker Vivianne Miedema, while Alessia Russo (two) and Frida Maanum were also on target for Jonas Eidevall's side.
There was no movement at all in the table on the final day of the season, as Bristol City - who were already condemned to relegation - went down 4-0 at home to eighth-placed Everton.
The Toffees' Merseyside rivals Liverpool - who finished fourth - ran out dominant victors by the same scoreline over Leicester City, while Tottenham Hotspur strolled past London rivals West Ham United 3-1.