Authorities have arrested the firebug accused of igniting a massive blaze inside of a Brooklyn nightclub earlier this month, Mayor Eric Adams announced Thursday.

John Lhota was busted by US Marshals for allegedly dousing the floor of Rash nightclub in Bushwick with gasoline before setting it ablaze on April 3 — sending panicked patrons running for the exits and severely damaging the venue, according to sources and federal court documents.

“We can confirm that the @FDNY, @NYPDNews and federal partners have caught the suspect in this arson and brought them into custody,” Adams tweeted Thursday afternoon, offering no further details. 

“We made a promise to our LGBTQ+ community and all communities to keep our city safe. We won’t rest in making that a reality,” he said.

It wasn’t immediately clear when Lhota was arrested for the club blaze. But he was fingered as the arson suspect last Friday — two days after he was arrested by police for allegedly assaulting a woman at his apartment, according to an arrest warrant affidavit.

The woman viewed the security footage of the arson and identified the suspect as Lhota, the court docs said.

The blaze at the LGBTQ-friendly bar sent two women — a bartender and a DJ — to the hospital. A bouncer, who briefly caught on fire, also sought medical treatment, according to the owners.

Before the fire, Lhota was captured on security camera footage leaving his apartment building, just a half mile away from the building, according to the court docs.

He was also seen purchasing a red canister, which he fills with gasoline, before allegedly “systematically pouring gasoline over the floor of Rash,” Craig Gundersen, an FDNY Fire Marshal, wrote in the arrest warrant affidavit.

Despite the heavy damage from the fire, one of Rash’s owners, Jack Sillen, told The Post the club will reopen “no matter how long it takes us.”

“Very little of [Rash] will be salvageable, we’ll have to start fresh,” Sillen said after the blaze.

“We spent the last year putting all of our time and energy and heart into this place and we were really proud of what it was becoming. It was only just getting on its legs.”

A GoFundMe campaign for the young club had raised a whopping $109,000 for a “Staff, Medical & Restoration Fund.”