A teen subway surfer is in critical condition after he fell off a moving Brooklyn train onto the tracks below Monday afternoon, cops said.

The 14-year-old boy was riding atop a northbound train on the J/M lines when he tumbled off the train car’s roof as it pulled into the Hewes Street station in Williamsburg around 3:40 p.m., police said. 

The thrill-seeking teenager was then knocked onto the rail line’s middle track, cops said.

EMS rushed to the scene and transported the teen to Bellevue Hospital in Manhattan, where he’s in critical condition, according to authorities. 

Another 14-year-old boy died in a subway surfing incident on the same subway line in May. 

He was killed while riding across the Williamsburg Bridge atop a J/M train while his 18-year-old pal was seriously injured.

Zemfira Mukhtarov, 12, and Ebba Morina, 13, were also killed while riding on top of a Brooklyn-bound J train last October, police said. 

Mukhtarov’s mother, Nataliya Rudenko, told The Post that she was heartbroken by the death of her daughter, who posted about her thrill-seeking adventures on TikTok.