Police are looking for a man who they say punched a 5-year-old boy in the face while on the subway.

The boy was riding a southbound G train with his mother just after 4 p.m. Saturday.

That's when police say the man, identified as Ramon Thomas, punched and taunted the child before fleeing at the Bergen Street station in Brooklyn.

The boy was taken to NYU Langone Health Cobble Hill with bruising and swelling on his face.

Thomas was last seen wearing a black jacket, green shirt, and cargo pants.

Police say he is about six feet tall, and weighs 180 pounds.

Anyone with information on the case should contact the Crime Stoppers hotline at 1-800-577-TIPS, or text CRIMES and then enter TIP577, or visit www.nypdcrimestoppers.com.