An unhinged assailant spat in a Queens straphanger’s face in an unprovoked attack this week — and then pummeled her when she tried to chase after him, authorities said.

The 32-year-old victim was on a Manhattan-bound E train approaching the 74th Street-Roosevelt Avenue station in Jackson Heights just before 10 a.m. Thursday when a stranger spat at her, police said.

When the suspect attempted to flee, the victim took off after him — prompting him to punch her in the head multiple times, police said.

The victim was treated at Elmhurst Hospital for head pain, and her attacker — captured in a surveillance photo released by police — remained at large Friday.