From left: Somerville Mayor Joe Curtatone, state Rep. Mike Connolly and former Boston City Councilor Tito Jackson at the State House in 2017. Photo courtesy of State House News Service.

Somerville Mayor Joe Curtatone announced Monday that he will not seek reelection.

The Democrat – who has held the office for nearly 18 years and is currently in his ninth term – is the longest serving mayor in the city’s history.

“This will be my final year as mayor of Somerville. It has been the honor of a lifetime to serve the city where I was raised. I love this job and this community with every ounce of my being,” he said during an address Monday.

Curtatone said he’s glad to be able to focus on continuing to lead the dense and rapidly changing city through the challenges of the coronavirus without the political distractions of a reelection campaign.

He vowed to be “all-in” throughout the rest of his final term.

Curtatone has adopted a more cautious approach to combatting the virus than the state as a whole, often keeping restrictions in place after they had been lifted for the rest of the state.

The 54-year-old has also been a regular critic of Republican Gov. Charlie Baker’s approach to reining in COVID-19, saying it has been too lax at times.

Curtatone, who has occasionally been mentioned as a possible candidate for governor in the past, declined to discuss future plans.

Baker has yet to say whether he will seek a third term next year.

The mayor oversaw a dramatic transformation of his city during his time in office, including the development of Assembly Row and the laying of plans to draw expansions of the booming biotech industry north from Cambridge’s Kendall Square, to the Union Square, Boynton Yards and Brickbottom neighborhoods along the Green Line Extension, as well as the XMBLY site next to Assembly Row.

Several million square feet of new office-lab developments are under construction, permitted or under review in the city. And a huge rezoning effort Curatone’s administration shepherded through before the COVID-19 pandemic took hold could bring new multifamily development into the city’s vibrant neighborhoods.

However, increasingly vocal anti-development factions and progressive “yes-in-my-backyard” pro-housing groups and have both emerged in city politics in recent years, raising questions about how the city’s next mayor will handle development issues.

Staff writer James Sanna contributed to this report.