A 13-year-old boy was stabbed by another teen about the same age today a Coney Island apartment today, authorities said.

The victim was inside the building on Ocean Parkway near Neptune at 4:29 p.m. when the other child allegedly stabbed him in the back, sources said.

The knife-wielding kid fled the scene and has not been arrested, police said.

The victim was taken to Lutheran Hospital, where he is in stable condition, cops said.