Police Commissioner Keechant Sewell has decided to discipline the NYPD’s highest-ranking uniformed officer after he was found to have abused his authority in a 2021 gun case — and he’s gearing up to fight the charges, The Post has learned.

NYPD Chief of Department Jeff Maddrey was served Tuesday with an official reprimand — saying he will be docked between five and 10 vacation days — for his role in voiding the arrest of a retired cop who was accused of flashing a gun at three children in Brooklyn in November 2021, according to internal affairs sources.

But Maddrey has indicated he’ll fight the punishment, according to the sources — setting the stage for him to square off against the police’s civilian watchdog, which substantiated the abuse allegations against him in April.

The Civilian Complaint Review Board had recommended that Sewell hit Maddrey with a “command B discipline” over the controversial incident.

Maddrey will take the matter to trial inside One Police Plaza, with the CCRB prosecuting the case. The police watchdog’s online database of charges showed the discipline was pending trial Wednesday.

A spokeswoman for the CCRB confirmed the agency would handle the case, but had no information about why the charges were heading to trial or how many days the commissioner had decided to dock the chief.

The CCRB found in its investigation that Maddrey had abused his authority by cutting loose Krythoff Forrester after the ex-NYPD cop was arrested on allegations he pulled a gun on three kids — ages 12, 13 and 14 — who smashed a camera outside his family’s realty office in Brownsville.

The youngsters said it was an accident.

Maddrey, who knew Forrester from his time as the 73rd Precinct commander, overruled the arresting sergeant on Nov. 25, 2021, personally showing up at the stationhouse late that night and ordering that the charges against the ex-cop be voided.

Forrester has denied pulling a firearm on kids. 

Maddrey, who was chief of community affairs at the time, also suggested the three kids involved be arrested instead, according to the CCRB’s report.

The Brooklyn District Attorney’s Office reviewed the incident and decided the chief’s actions were not criminal. 

An attorney for the three boys has called on Maddrey to resign.

Mayor Eric Adams has defended the officer, saying he was “proud” that Maddrey was his chief of the department.

A spokesperson for NYPD said it does not comment on active disciplinary matters. 

“We are looking forward to his complete exoneration,” Maddrey’s attorney, Lambros Y. Lambrou, said.

He denied that his client had been disciplined by Sewell, saying, “Chief Maddrey has not been disciplined related to the CCRB findings of April regarding retired Officer Forrester.”

Under the NYPD’s disciplinary process,the police commissioner can either agree with or diverge from a recommendation for discipline from the CCRB following a substantiated complaint.

The commissioner would then issue the discipline to the officer involved, and in some instances, the cop can either accept the punishment or take the case to an internal trial to fight the charges.