David Cassidy -- Pleads GUILTY to DWI

David Cassidy copped a plea in his felony drunk driving case in NY, and got the charge reduced to misdemeanor DWI.

Cassidy was in court Wednesday to enter a guilty plea. Under the terms of the deal he has to complete 50 hours of community service and have an ignition interlock installed on his car. He's already completed an alcohol treatment program, but in November the judge will decide if he needs more ... according to the D.A.

Cassidy was arrested last year after he was stopped by cops in Schodack, NY, and tests showed his blood alcohol level was 0.10 ... way over the legal limit of .08.