Nassau Veterans Memorial Coliseum (or simply the Nassau Coliseum) is a multi-purpose indoor arena in Uniondale, New York, east of New York City.

Opened in 1972, the Coliseum occupies 63 acres (25 ha) of Mitchel Field, a former Army airfield, later an Air Force base. The facility is in the Town of Hempstead, within the Uniondale 11553 ZIP code. The Coliseum is used for sporting events, concerts, large exhibitions and shows as well as trade shows—44,000 square feet (4,100 m2) at the main arena, 60,000 at the Expo Center. In 2015, the arena was closed for a major renovation which was completed in April 2017.

The New York Islanders of the National Hockey League (NHL) played at the Coliseum from 1972 to 2015 before moving to Barclays Center in Brooklyn. After the move was commercially unsuccessful, the team split its home schedule between Barclays and the renovated Coliseum from 2018 to 2020 and played the home portion of their 2020–21 season at the Coliseum, before moving to the new UBS Arena at Belmont Park for the 2021–22 season, which is also on Hempstead Turnpike, 7.7 miles (12.4 km) west of the Coliseum.

It was also the home of the New York Nets (now known as the Brooklyn Nets) of the American Basketball Association (ABA) and National Basketball Association (NBA) from 1972 to 1977. In 2017, the venue became the new home of the Brooklyn Nets' NBA G League team, the Long Island Nets. Currently, the New York Riptide of the National Lacrosse League and the Nets serve as the building's main tenants.