A 17-year-old boy was stabbed in the leg with a knife on a Brooklyn subway Friday night for asking other teens to turn their loud music down, cops said.

The teen was on a northbound R train entering Union Street Station on Fourth Avenue in Park Slope around 9:30 p.m. when he asked three other teenagers to turn the blaring beats down, cops said.

“They took umbrage,” a police spokesman said. “He’s stabbed in the leg.”

The teens fled the train after the stabbing. The 17-year-old who was stabbed in his thigh was taken to Methodist Hospital in stable condition.

There were no arrests.