Skidmore, Owings and Merrill LLP (SOM) is an American architectural and engineering firm that was formed in Chicago in 1936 by Louis Skidmore and Nathaniel Owings; in 1939 they were joined by John O. Merrill. They opened their first branch in New York City, New York in 1937. SOM is one of the largest architectural firms in the world. Their primary expertise is in high-end commercial buildings, as it was SOM that led the way to the widespread use of the modern international-style or "glass box" skyscraper. They have built several of the tallest buildings in the world, including the John Hancock Center (1969, second tallest in the world when built), Sears Tower (1973, tallest in the world for over twenty years), and Burj Khalifa (2010, current world's tallest building). SOM provides services in Architecture, Building Services/MEP Engineering, Digital Design, Graphics, Interior Design, Structural Engineering, Civil Engineering, Sustainable Design and Urban Design & Planning.

Many of SOM's post-war designs have become icons of American modern architecture, including the Manhattan House (1950), designated as a New York City landmark in 2007 by the New York City Landmarks Preservation Commission, and the Lever House (1952), also in New York City; as well as the Air Force Academy Chapel (1958) in Colorado Springs, Colorado; and the John Hancock Center (1969) and Sears Tower (1973), both in Chicago.

Although SOM was one of the first major modern American architectural firms to promote a corporate brand, many famous architects, engineers and interior designers have been associated with the various national offices.

Well-known SOM architects include Gordon Bunshaft, Adrian Smith and David Childs. The earliest amongst the many engineers that worked at SOM was John O. Merrill. Fazlur Khan, another engineer, is considered one of the greatest structural engineers of the second half of the 20th century. He is best known for his constructions of the Willis Tower (formerly the Sears Tower), and John Hancock Center and for his designs of structural systems that remain fundamental to all high-rise skyscrapers. Another notable SOM engineer is Bill Baker, who is best known as the engineer of Burj Khalifa (Dubai, 2010), the world's tallest man-made structure. To support the tower's record heights and slim footprint, he developed the "buttressed core" structural system, consisting of a hexagonal core reinforced by three buttresses that form a Y shape.