The title race went to the last weekend of the season following Manchester United's late win over local rivals Manchester City last weekend. Chelsea's 2-0 win over Arsenal earlier in the day last Sunday, meant Emma Hayes' side held a two-point advantage heading into the final weekend of the season.
It sees Chelsea complete the double -- their fifth under Hayes -- after they won the Women's FA Cup on May 14 with a 1-0 win over United. It continues their remarkable dominance of English football with Emma Hayes' side winning their 13th major trophy since Hayes took charge in 2012.
"This has definitely been the hardest year for me and I feel relived it's over for lots of reasons," Hayes told a postmatch news conference. "I feel sad because winning the league and relegating a friend, doesn't feel good in my soul and who I am."
Hayes, who has been in charge at Chelsea since 2012, underwent an emergency operation for endometriosis in October.
It has been a turbulent campaign for Chelsea's playing staff, too, with injuries to key personnel at various stages.
Pernille Harder was out from November through to May, while Fran Kirby has been out since February. Millie Bright joined her England teammate on the sidelines after she picked up a knee injury in March. Katerina Svitkova has been out since February, while Kedeisha Buchanan picked up an injury in April.
Despite the host of absentees, Chelsea managed to maintain a title challenge while also battling for the FA Cup and Champions League. They fell at the semifinal stage of the European competition against Barcelona, losing 2-1 over two legs, but were widely praised for valiant performances across both legs.
Sam Kerr has starred for Chelsea and was crowned Football Writers' Player of the Year in May in recognition of her 10 goals and match-winning performances. It was also Lauren James' breakout season as her club form saw her establish herself as an England regular.
Information from ESPN's Sophie Lawson contributed to this report.