A Bronx man drowned at Rockaway Beach last night while his girlfriend watched in horror, authorities said.

Oscar Cruz, 22, of the Tremont section of The Bronx went into the ocean off Beach 116th Street near Rockaway Beach Boulevard just after 8 p.m. Lifeguards had already left their stations.

Cruz was swept beyond the breakers before being pulled out by FDNY rescuers, according to officials.

The victim’s horrified girlfriend watched while her unconscious beau was carried ashore and rushed to Peninsula General Hospital where he was later pronounced dead, sources said.