370 Jay Street, Modern office building in Downtown Brooklyn, United States

370 Jay Street is a 13-story modern office building located at the intersection of Jay Street and Willoughby Street in Downtown Brooklyn. Its facade features white limestone cladding with uniform casement windows arranged in symmetrical rows across the entire structure.

370 Jay Street was built by the New York City Board of Transportation as its headquarters, designed by William Haugaard and Andrew J. Thomas; the pre-war Art Deco scheme became a post-war modernist building. After 1953 it housed the New York City Transit Authority and then the MTA, which vacated it gradually from 1990. In 2012 NYU agreed with the MTA to take over and restore the building, moving in from 2017.

The building's name comes from its address at Jay and Willoughby Streets, and its subway entrances keep the original Art Deco/Art Moderne lamp posts installed with the building. The Jay Street–MetroTech complex entrances sit within both ground-level arcades, and the south arcade has an elevator down to the station.

Subway entrances sit inside both ground-level arcades and beside the building, linking to the Jay Street–MetroTech complex; the south arcade has an elevator down to the platforms. The building's loading dock and basement garage entrance are at the north end of Pearl Street. Myrtle Avenue's old right-of-way is now the pedestrian Brooklyn Renaissance Plaza.

The building's site was chosen so that its basement could connect by passageways to all three subway divisions (IRT, BMT, IND), letting money trains deliver fares to a sorting room below ground. A visible door in the Jay Street IND station still marks one of those passages. Armored trucks replaced the money trains in 2006.