The Art Gallery of Hamilton (AGH) is an art museum located in Hamilton, Ontario, Canada. The museum occupies a 7,000 square metres (75,000 sq ft) building on King Street West in downtown Hamilton, designed by Trevor P. Garwood-Jones. The institution is southwestern Ontario's largest and oldest art museum.

The museum was established as the Municipal Gallery of Hamilton in January 1914, and was opened to the public in June 1914, at a Hamilton Public Library building on Main Street West. The museum continued to operate from that location until 1953, when the museum relocated to a new building in the neighbourhood of Westdale. In 1977, the museum moved to its present King Street West location. The museum building was renovated with designs by Bruce Kuwabara from 2003 to 2005.

The Art Gallery of Hamilton's permanent collection has over 10,000 works by artists from Canada, and around the world. In addition to exhibiting works from its collection, the museum has also organized, and hosted a number of travelling exhibitions.

The spouse of William Blair Bruce donated a number of works to the City of Hamilton, on the condition that an adequate facility was founded to house them. The museum was formally incorporated by the city on 31 January 1914 as the Municipal Gallery of Hamilton. The museum first operated from the second floor of a Hamilton Public Library branch on Main Street, west of James Street. The museum was opened to the public on 28 June 1914, hosting an exhibition 33 works by William Blair Bruce.

In 1947, the raised the budget of the institution significantly, and the employment of the institution's first curator-director, Thomas Reid MacDonald. MacDonald had sought to grow the institution's collection, as well as refurbish, or construct a new museum's building. During this time, an auxiliary volunteer group to support the museum, known as the Women’s Volunteer Committee. The Committee helped raise funds for the acquisition of works, as well as funds for a new building. On 12 December 1953 the museum opened a one-storey Art Deco building in the neighbourhood of Westdale, adjacent to McMaster University.

However, by the 1960s, it had become apparent that any expansion of the museum would requiring relocation, as expansion plans for the adjacent university made any plans to expand the museum difficult. The museum eventually announced its plans to relocate to downtown Hamilton, as a part of the municipal government's larger "Civic Square Project;" which included Hamilton Convention Centre, and Hamilton Place (later renamed FirstOntario Concert Hall). Trevor Garwood-Jones was commissioned to design a new building for the museum, and was opened in October 1977.

In 2003, the museum underwent C$18 million renovation of the building. The renovated museum building was reopened in May 2005.

The museum was notified in 2003 that a painting in its permanent collection, Portrait of a Lady, by Johannes Cornelisz Verspronck, was suspected of being art stolen by the Nazis during World War II. After a 10 year investigation into the claim, the museum confirmed the claim in November 2014, and returned the painting to its original owners. The painting was acquired by the museum at a Sotheby's auction for C$58,000 in 1987; with the museum unaware that the work was stolen art.