It was Arsenal's first title since 2012 and their third overall, making the London side the most successful team in the league since it was formed in 2011.
Vivianne Miedema scored her 22nd goal of the season in the sixth minute before creating the second for Katie McCabe at the half-hour mark. Beth Mead and Danielle van de Donk scored in the second half to seal the title for Joe Montemurro's side.
"I came to Arsenal to win the league but I don't think I've realised what we've done yet," Miedema said after the win.
"I'm happy we've done it and we've done it with a 4-0 win. Joe changed a lot when he came in, so he has to take a lot of credit, but more than anything he really made us believe in ourselves."
Arsenal play their final game against Manchester City on May 11.
(Reporting by Rohith Nair in Bengaluru, editing by Pritha Sarkar)
