A couple was found dead in an apparent murder-suicide in an Upper West Side building this morning — discovered by the slain woman’s teenage son, cops said.

Police were called to the dwelling in the cheap single-room-occupancy building on Riverside Drive and West 94 Street around 11:45 a.m., cops said.

Edwin Rodriguez,58, was found on a bed with a belt wrapped around his neck, and his girlfriend, Florenciana Martinez,44, was found nearby on the floor with trauma to her face, law-enforcement sources said.

Martinez’s 19-year-old son made the grisly discovery, the sources said.

It was unclear what sparked the violence, and the Medical Examiner’s Office will determine the cause of death, cops said.

Rodriguez was married to another woman but would spend time with Martinez at the UWS apartment, the sources said.