Hit-and-run drivers slammed into three bicyclists in two separate incidents early Saturday across two boroughs, killing one and injuring two–— including a man who was struck across the street from a hospital, police said.

In Manhattan at around 1:30 a.m., an unknown motorist was driving a dark-colored sedan that slammed into two men –— possibly cousins — riding on the same bike at the intersection of Amsterdam Avenue and West 99th Street on the Upper West Side, authorities said.

The driver drove off, north on Amsterdam, cops said. Responding police officers found the victims, a 28-year-old and 19-year-old with body trauma. EMS transported both men to Mt. Sinai-St. Luke’s Hospital, where the older man was pronounced dead.

The 19-year-old was listed in stable condition, cops said.  

The probe is ongoing by the NYPD’s Highway Patrol Collision Investigation Squad. The name of the deceased is being withheld pending family notification.

A little more than two hours later in Brooklyn, at 3:50 a.m., a 63-year-old bicyclist was seriously injured after being struck by a hit-and-run motorist in at 1 Brookdale Plaza– across the street from the emergency room of Brookdale Hospital on Linden Boulevard and Rockaway Parkway, police said.

The driver fled the scene and the victim was admitted to Brookdale in critical condition, police said.