In front of a WSL record crowd of 59,042, Alessia Russo scored twice as the Gunners produced a brilliant performance to blow the title race open.
Beth Mead gave Arsenal the perfect start with a goal after eight minutes but Chelsea responded to equalise against the run of play through Johanna Rytting-Kaneryd.
Amanda Ilestedt put Arsenal back in front and Russo made it 3-1 with a cool finish before half-time.
Chelsea never really looked like getting back into the game and Russo added a fourth goal from the penalty spot in the second half.
Arsenal manager Jonas Eidevall said: “When we played Chelsea here two and half seasons ago I was knee sliding as that felt big. Now what is important is the table at the end of the season, let’s not get carried away. It does not count if we are not ready for against Tottenham. We need to be focused for that.”
Chelsea manager Emma Hayes said: “They were extremely clinical and I felt like we got bullied in the duals all over the pitch. I am not going to make excuses I will speak to the players tomorrow about it. We were well and truly beaten. We have to get back to our standards. That was not our Chelsea standard and we have to control what we control.”
