David Cassidy -- Arrested for Drunk Driving ... AGAIN!

David Cassidy was arrested Friday night for driving drunk ... TMZ has learned.

David had just exited the 405 freeway in LA when cops say they saw him make an illegal right onto a surface street ... this according to law enforcement sources.

The cop approached the vehicle and says he smelled alcohol. He ordered David out of the car and administered a field sobriety test ... which David flunked.

To make matters worse, David blew .19 ... more than twice the legal limit.

Cassidy was hauled off to jail, booked for driving under the influence and released hours later.

If this sounds like the same old song ... it is. David was arrested last year in New York for DUI ... as well as once in Florida back in 2010.