The Hudson River Museum, located in Trevor Park in Yonkers, New York, is the largest museum in Westchester County, and features the only public planetarium in the county. While often considered an art museum due to its extensive collection of Hudson River School paintings, the museum also presents exhibits on the history, science and heritage of the region.

Founded in 1919 as the Yonkers Museum, the facility was also known as the Yonkers Museum of Science and the Arts, prior to being named the Hudson River Museum. The museum originally contained a number of mineral specimens housed in Yonkers City Hall. Photographer Rudolf Eickemeyer Jr., a lifelong resident of Yonkers, played a key role in the creation of the museum, as did sculptor Isidore Konti, and George J. Stengel.

Central to its history is the Glenview Mansion, a house built in 1877 from a design by American architect Charles W. Clinton, and once the home of one John Bond Trevor. Home of the museum for 45 years from 1929, the house now forms a large part of the Hudson River Museum. It contains six period rooms displaying furniture and decor from that era. In 1972 it was listed on the National Register of Historic Places. The Museum is accredited by the American Alliance of Museums, a mark of excellence it has maintained since 1974. The rooms on public display feature carved woodwork by Philadelphia cabinetmaker Daniel Pabst.

In 1979, artist Red Grooms created and installed "The Bookstore" at Hudson River Museum, where it is on permanent display.

The museum has had a planetarium component for over 60 years. The first planetarium was constructed in 1956 inside the Glenview mansion dining room. It had a 20-foot dome, seating for 50 and a Spitz A-1 star projector. In 1969, as part of a major expansion of the museum campus, a planetarium was built with a 40-foot dome, seating for 120 and a Spitz Space Transit Projector. In 1987 the Spitz was replaced by a Zeiss M1015 star projector. One of only three in the U.S., it was capable of displaying 5,000 stars, a thousand more than the Spitz.

In 2014 the planetarium was renovated and upgraded with a Sky-Skan Digital Planetarium system and a Megastar projector capable of displaying 22 million stars. The Hudson River Museum Planetarium (formerly known as the Andrus Planetarium) remains the only public planetarium in Westchester County, and one of the few in the region to feature live presenters on weekends in addition to pre-recorded shows. The planetarium accommodates school groups on weekdays, while three different shows are offered to the public on weekends. Special events and shows are occasionally presented in the evening. The museum has also hosted watch parties for many astronomical events, beginning in 1971 with the close approach of Mars, to Halley's Comet in 1986 and the solar eclipses of 2017 and 2024.

The planetarium was one part of the museum's expansion throughout the 1960s, which also included the construction of larger and more modern facilities to house its collections, followed by the restoration of the ground floor of the Glenview house to its 19th-century condition.

The museum's diversity is part of what led to its citation as one of the most unusual cultural facilities by the New York State Council on the Arts in 1972. It has sought to maintain this diversity amidst changes in leadership and focus throughout its history. The diversity is apparent in the museum's 23-acre (9.3 ha) site, on which a 2006 expansion attempted to better join the Glenview Mansion with the modern 1969 additions.

The museum used its namesake, the Hudson River, as the core of its 75th anniversary celebration in 1994. It celebrated its centennial in 2019.

Since 1995 the museum has offered a Junior Docent Program; the program was recognized by the President's Committee on the Arts and Humanities with a Coming Up Taller Award in 2008.

In November 2020, the museum broke ground on an expansion project, adding a 12,000 sq ft (1,100 m) wing to the campus. The new West Wing debuted in June 2023 and houses special exhibition spaces overlooking the Hudson River, a 100-seat auditorium, a Community and Partnership Gallery, and art storage space, also allowing the museum to display more of its permanent collection. In 2023, the museum was awarded a federal Museums for America grant from the Institute of Museum and Library Services to digitize approximately 8,000 objects, largely consisting of historical photographs representative of their local and regional communities, including photographs from the archives of the John Bond Trevor family, the Alexander Smith Carpet Factory, artist Alvin Hollingsworth, and photographer Rudolf Eickemeyer Jr.

The period interiors of the museum's Glenview Mansion appear in the HBO series The Gilded Age, an American historical drama television series created by Julian Fellowes, which premiered in January 2022.

The late 1980s was a difficult time for the Hudson River Museum when it faced a decrease in funding, uncertainties in future funding, and a high level of staff turnover. The museum was forced to reduce its operating hours and cut some programming, but was able to expand the planetarium. The facility experienced a resurgence in the 1990s, received a number of grants and awards, saw increased funding from Westchester County, and was able to expand in time for its 75th anniversary. The museum also saw its attendance almost double from 55,000 to 100,000 between 1990 and 1994. The late 1990s saw a downturn in funding and the museum was again forced to face significant cutbacks. In the wake of these cutbacks, the museum began to host private events and offer tours, particularly to groups of school children, as a means of increasing income.

• Hudson River Museum