Another day, another brawl on Muni.

And a pen acted as a weapon in the latest incident, cops said.

It was a two-on-one fight between girls who had “run-ins” before, police said, with the onboard scuffle happening around 2:30 p.m. Wednesday at Geneva Avenue and Paris Street in the Excelsior district.

The victim told responding cops that one girl “used a pen to stab and poke” at her while the other girl stole stuff from her purse, police said.

The cops later caught up with the suspects, and while the stolen property wasn’t found, they charged the girls with assault, police said.