945 Madison Avenue

945 Madison Avenue, also known as the Breuer Building, is a museum building on the Upper East Side of Manhattan, New York City. Built from 1964 to 1966 as the third home of the Whitney Museum of American Art, it subsequently held a branch of the Metropolitan Museum of Art and the Frick Collection before becoming the headquarters of Sotheby's auction house. Marcel Breuer and Hamilton P. Smith were the primary architects, with Michael H. Irving as the consulting architect and Paul Weidlinger as the structural engineer. 945 Madison Avenue was Breuer's most significant design in New York City and one of the most important of his career. It was also his first museum commission, and his first and only remaining work in Manhattan.

The building sits on a 13,000-square-foot (1,200 m²) site at Madison Avenue and 75th Street that was once occupied by six 1880s rowhouses. The building is usually described as part of the Modernist art and architecture movement, and is often described as part of the narrower Brutalist style. The structure has exterior faces of variegated granite and exposed concrete and makes use of stark angular shapes, including cantilevered floors progressively extending atop its entryway, resembling an inverted ziggurat.

Ideas for the building began in the 1960s, when the Whitney Museum sought a new building three times the size of its existing facility. The Whitney occupied the building until 2014, during which, the surrounding area evolved from an elegant residential neighborhood to an upscale commercial hub. In 2016, the museum building was leased to the Metropolitan Museum of Art and became the Met Breuer; the new museum contributed to the neighborhood's transformation but closed in 2020. From 2021 to March 2024, the building became the Frick Madison, the temporary home of the Frick Collection while the Henry Clay Frick House underwent renovation. In 2023, Sotheby's purchased 945 Madison Avenue and announced plans to use the building as its global headquarters.

The design was controversial, though lauded by notable architecture critics at its opening. The building defined the Whitney Museum's image for nearly 50 years, influencing subsequent projects such as the Cleveland Museum of Art's north wing and Atlanta's Central Library. Breuer's design also influenced the new Whitney Museum building in Lower Manhattan by Renzo Piano, with both buildings featuring cantilevering floor plates and oversized elevators. The structure and surrounding buildings contribute to the Upper East Side Historic District, a New York City and national historic district, and the exterior and parts of the interior are New York City designated landmarks.