Mayor-elect Zohran Mamdani has named his administration’s incoming fire commissioner — just one hour before outgoing Mayor Eric Adams swore in his own pick for the job.

Mamdani announced Lillian Bonsignore's appointment at 1 p.m. The 31-year FDNY veteran led the department's emergency medical services through the COVID-19 pandemic.

Then, at 2 p.m., Adams held a ceremony to swear in Mark Guerra, a 36-year department veteran and first deputy commissioner, as fire commissioner — an appointment that will last only until Mamdani takes office Jan. 1.

Adams defended the timing, saying public safety "doesn't go on holiday." Guerra will succeed — if only briefly — FDNY Commissioner Robert Tucker, who submitted his resignation the day after Mamdani’s election, effective Dec. 19.

"If you look at the beginning of my time in office, we had a horrific fire that took the lives of a large number of Bronxites," Adams said, referring to a 2022 blaze that killed 17 people and happened nine days into Adams' term.

Laura Kavanagh, whom Adams kept as acting Fire Commissioner for 10 months before swearing her in as full commissioner, praised Mamdani’s pick of Bonsignore and pointed to her understanding of the FDNY’s B-HEARD program, which sends mental health care workers to some 911 calls. Mandani supports the program.

“I saw firsthand Chief Bonsignore’s lifelong dedication to the FDNY, including her work on the front lines of COVID and in advocating for long-overdue EMS pay raises,” she said. “Mayor-elect Mamdani has made a terrific choice for the FDNY and for all of us who rely on the greatest fire department in the world to keep our city safe.”

Guerra, who joined the FDNY as a firefighter in 1988, has been cited for bravery four times during his career. He holds degrees in mechanical engineering and law.

Bonsignore was the highest-ranking uniformed woman in FDNY history and the first woman to achieve a four-star rank. In 2019, she became the first woman and first openly LGBTQ+ individual to serve as chief of EMS operations in the department's 155-year history.

As chief, she oversaw more than 4,300 EMS providers responding to approximately 1.5 million calls annually and led EMS through the pandemic's unprecedented call volumes.

"Bonsignore's calm, decisive leadership during the COVID-19 pandemic — when EMS professionals were more vital than ever — is exactly the kind of leadership our city needs," Mamdani said.

Her appointment comes as EMS workers remain locked in a years-long contract dispute over pay. EMTs can earn as little as $36,330 starting, compared to $54,122 for firefighters. After five years, paramedics top out at $76,028, while firefighters can make more than $105,000.

EMS unions have filed a class-action discrimination lawsuit against the city, alleging the pay disparity stems from bias against EMS workers, who are predominantly women and people of color.

Adams campaigned on bringing pay parity to EMTs and paramedics, but will leave office without fulfilling that promise.

The Uniformed Firefighters Association did not immediately return a request for comment on Bonsignore's appointment.

Mamdani also announced that Sanitation Commissioner Javier Lojan and Emergency Management Commissioner Zachary Iscol will remain as interim commissioners during the snow season.

This story has been updated with more information.