Friday night lights have a dark side in Sleepy Hollow.

The Westchester town has possibly the nation’s spookiest high school mascot – a Headless Horseman who leads the football team onto to the gridiron in a nod to Washington Irving’s epic tale, “The Legend of Sleepy Hollow.”

“Adrenaline starts pumping. That’s when you just lock in,” Sleepy Hollow’s starting quarterback Jeremiah Bowen described to The Post, of sprinting out with the beloved equestrian tradition of nearly two decades.

In a pre-game ritual that has gone viral online, the black-caped horseman — whose identity is a closely guarded school secret — leads the Sleepy Hollow football players out out of a nearby forest and onto the field.

As the terrifying mascot rides in at full gallop, a remix of the Michael Myers “Halloween” theme blares on the speakers.

“When you step on that field, you know it’s go time,” added the QB who scored two touchdowns under full moonlight last Friday.

The fans also love the unique tradition.

“We can’t stop doing it because people expect it,” said Horsemen booster club president Justin O’Leary, whose son Sutton is a lineman. 

“It’s even exciting for other teams. I think being part of it and seeing it might be a little intimidating, which I think is the point.”

The booster club and supportive local businesses fund the $500 to $1,000 per night cost to bring the black horse from Warwick’s Corinthian Equestrian Center to each home game.

Corinthian uses a roster of a few different equines — last week’s was one named Marley — and keeps the rider’s identity a mystery.

The anonymous owner said Marley loves interacting up close with the crowd while trotting the sidelines between breaks of grubbing on the hill’s grass.

The feeling is mutual with the fans and students.

“I personally love it,” said cheerleader Sophia Blanchard, who added that the squad knows not to startle the horse with their pom-poms.

“We definitely do Halloween the best,” she added. “It’s for sure our favorite holiday.”

“I meet people from all over – I met somebody from California. I love that they come, that they enjoy it, and they treat it with respect.”

The 12th grader is one of many local kids who grew up “really familiar” with Irving’s 1820 short story and the plight of its protagonist, lanky school master Ichabod Crane; who is half-scared to death during a horseback chase with a phantom Revolutionary War Hessian soldier at a bridge frequented by visitors.

“We definitely have done some English assignments on the legend,” said fellow senior cheerleader Danise Garcia.

Sleepy Hollows’ only rival for mascot spookiness is Salem, Mass. High School, whose teams are known as The Witches after the infamous witch trials held there in the 1600s.