A man fell onto the tracks at Grand Central Station while fighting with another straphanger early Sunday, police said.

The men began fist fighting on the 4 train platform before one of the combatants was knocked onto the roadbed around 2 a.m.

Some good Samaritans jumped down onto the tracks and helped the man back up onto the platform and called police.

Responding officers arrested the assailant, identified as Charles Cruz, 43, at the scene and charged him with assault.

It’s unclear what started the fight, police said.