An MTA bus driver was assaulted in lower Manhattan last night by a man who punched her in the face and snatched her purse, cops and union sources said.

The M-14 bus was heading southbound on the service road near the FDR Drive between East Houston and Delancey streets when the thug boarded at the second-to-last stop at 8:30 p.m., according to cops.

He socked her in the face twice and snatched her purse before fleeing the scene, the sources said.

Cops early this morning were searching for the suspect.

The driver was being treated at New York Downtown Hospital.