These kids have gone off the rails.

A group of MTA-obsessed thrill seekers are turning the subway system into their own perilous playground, transit sources told The Post.

The self-described “Subway Conquestors,” — a rogue offshoot of normally mild-mannered transit enthusiasts — is breaking into subway cabs, surfing atop trains, trespassing in abandoned stations, and stealing and tampering with MTA signage.

New videos obtained by The Post reveal the reckless subway junkies roaming around an deserted section of the Canal Street stop, as well as at the Bergen Street and 9th Avenue stations in Brooklyn.

Subway surfing videos at the old City Hall stop were also posted online.

And alarming pictures taken by one Keyshawn Brown — busted in March for sparking an explosion on the rails at the Nostrand Avenue A/C train station — show stolen MTA keys and a worker’s vest on his bed.

“#AllWeNeedIs1moreKey,” Brown boasted on Facebook.

A transit source said the behavior is fueled in part by social media and smartphone use, as the crew aspires to document their hijinks and one-up themselves.

Law-abiding transit buffs are policing themselves — by booting the vandals from online forums and sending about a dozen photos and videos to Crimestoppers.

But so far, only Brown has been arrested.

Riders should contact an MTA worker or cop if they witness any illegal activity, and the authority will also take photos and videos of such activity, an MTA spokesman said.

Meanwhile, there has been a spike in the number of unruly riders causing irritating delays in the transit system.

New data from the latest month available from the MTA showed a 75 percent uptick on weekdays in delays caused by out of control straphangers– and almost 340 percent on weekends in February 2015.

Recent episodes that snarled service include a nude rider who spat on a 1 train conductor at the Chambers Street station, fighting at the 86th Street station, and subway surfing on the 110th Street stop on the 6 line.

A transit source said the 6 train has had the most of these low riders– who disrupted service on the line almost 1800 times this year.

The 4 has also struggled with straphanger mayhem, with almost 900 unruly rider delays.

Sources added that March saw an uptick in unruly rider delays as well. April saw a decrease in the number of incidents, but overall time lost to delays went up.