Notoriously tardy Mayor Bill de Blasio actually showed up early for jury duty at Manhattan Criminal Court on Wednesday.

The mayor, who postponed a previous jury notice six months ago, arrived at 100 Centre St. at 9 a.m., a half-hour before he had to sign in, and passed through a metal detector just like other members of the public.

Video footage posted on Twitter drew a chuckle from former City Council Speaker Melissa Mark-Viverito, who was ready to take action that he’d be out in less than two hours.

“Jaja!!! Yeah, right. Jury duty. Sure he will be selected! Out before 11 am. Any other bets?” she tweeted.

However, de Blasio wasn’t spared such a reprieve.

Around 11 am, his name was called and de Blasio was escorted to the courtroom of Judge Laura Ward to potentially serve on a gun-charge case. While there, he was known as “Number 12” among the group of potential jurors.

He was able to get out of serving on that case after explaining he expected to be out of town during the trial. Hizzoner was brought back to a jury waiting area to potentially be selected for another case.

Throughout the morning, de Blasio conversed with many other prospective jurors, including the top editor of a local Bronx newspaper.

“I said to him, ‘I have to serve too.’ He said, ‘I guess we all have to serve. It’s a great equalizer,’” recalled David Cruz, 35, editor-in-chief of the Norwood News.

“I was surprised to see him — in a city of 8 million … I can’t believe he’s serving at the same time I am,” added Cruz. “I thought he was going to talk his way out of it. I give him credit. He sat in the front row waiting to serve like everybody else.”

Kariné Poghosyan, a pianist, shook hands and thanked de Blasio for recently taking time to write back and say he couldn’t attend a concert she had invited him to.

“He asked me how it went. I said, ‘great! I had a standing ovation,’” said Poghosyan.

“It’s wonderful he’s here. I’m in a better mood after seeing him. I came in grumpy because I have practicing to do, and then he walked in. I thought, okay he’s leading the way, let’s follow suit.”

Scarlett Wittman snapped a selfie with the mayor. Others grabbed the chance to chat with Hizzoner, who was stuck with them in the jury room.

Things weren’t all smooth for the mayor. The courthouse misspelled his name “Deblasio” on a form, so he had to cross it out and correct it.

By late afternoon, de Blasio and most of the other prospective jurors were dismissed.

Three years ago, first lady Chirlane McCray tried to get out of jury duty by claiming she had a hectic schedule. She ultimately showed up for two days in October 2015 without getting picked.

De Blasio and his wife, both longtime residents of Park Slope in Brooklyn, now reside at Gracie Mansion in Manhattan.

In 1999, Rudy Giuliani became the city’s first sitting mayor to serve jury duty while in office.

The former prosecutor ultimately was tapped as jury foreman in a $7 million Manhattan civil case brought by a Harlem man who sued his landlord, claiming his genitals were burned by scalding shower water.

Giuliani and his fellow jurors rejected the lawsuit.

In 2016, former Mayor Mike Bloomberg briefly served jury duty some two years after leaving office.

When Justice Laura Ward asked him what he did for a living, the billionaire replied nonchalantly, “I manage my company — a financial information company.”