An MTA track worker was struck and killed by a train at the Herald Square subway station early Wednesday morning, authorities said.

Police said the 57-year-old man was hit by a northbound D train while working on the tracks just before 12:30 a.m. He was taken to Bellevue Hospital, where he was pronounced dead, the NYPD said.

Transport Workers Union Local 100, which represents thousands of city transit employees, identified the worker as Hilarion Joseph.

"Our folks were at the hospital last night with the worker's family. And obviously, they're very much in our thoughts right now,” MTA president and CEO Janno Lieber said at a board meeting Wednesday morning. “So difficult morning for, most of all, for those close to our colleague."

The MTA halted all nonessential work after the incident, Lieber said. An investigation is ongoing.

At a news conference Wednesday afternoon, TWU Local 100 secretary-treasurer and director of safety John Chiarello called Joseph’s death a “tragic incident.”

Joseph was days away from celebrating a year with the MTA when he was struck, Chiarello said.

“This development has shaken our union, and our deepest condolences go out to the family, friends and colleagues during these incredible times,” he said.

The union will take “every necessary measure to prevent such tragedies in the future,” he added.

In a statement posted to social media, Mayor Eric Adams said his “prayers are with the family of the track worker and his fellow colleagues.”

“Our track workers work hard to keep our subways — the lifeblood of our city — running at all hours of the day,” he wrote. “We must continue to do everything we can to make sure they are safe.”