24 Sussex Drive, originally called Gorffwysfa and usually referred to simply as 24 Sussex, is the official residence of the prime minister of Canada, in the New Edinburgh neighbourhood of Ottawa, Ontario. Built between 1866 and 1868 by Joseph Merrill Currier, it has been the official home of the prime minister since 1951. It is one of two official residences made available to the prime minister, the Harrington Lake estate in nearby Gatineau Park being the other. 24 Sussex has not been an actual residence since 2015.

The house at 24 Sussex Drive was originally commissioned in 1866 by lumberman and Member of Parliament Joseph Merrill Currier as a wedding gift for his wife-to-be Hannah Wright. It was completed in 1868 and Currier named it Gorffwysfa (Welsh for 'place of rest'). It was sold for $30,000 in 1901, after Hannah Currier's death, to William Edwards.

In 1943, the Government of Canada used its power of expropriation to divest Gordon Edwards, nephew of William Edwards, of his title to the house, to consolidate Crown ownership of the lands along the Ottawa River. Edwards had fought the action, but eventually lost the dispute with the Canadian government in 1946 and died at the house later that year.

After several years of uncertainty, the government decided in 1950 to refurbish the property as a residence for the prime minister, the renovations costing just over $500,000. Previous prime ministers lived at a variety of locations around Ottawa: Wilfrid Laurier and William Lyon Mackenzie King, for instance, lived at Laurier House in Sandy Hill. Laurier House was willed to the Crown upon Mackenzie King's death in 1950 and was thus also available for designation as the prime minister's official residence at the time.

Louis St. Laurent was the first to take up residence at 24 Sussex Drive in 1951. Since then, every prime minister has resided at 24 Sussex for the duration of their times in office, with two exceptions. Kim Campbell resided at Harrington Lake during her brief term, as her predecessor Brian Mulroney remained at 24 Sussex temporarily (despite having resigned as prime minister, as per agreement with Campbell) pending renovations of his Montreal home; Campbell's government was defeated in the 1993 Canadian federal election on 25 October 1993 (had Campbell won that election then she would have moved into 24 Sussex). Although it was his childhood home when his father was Prime Minister, Justin Trudeau has opted to reside at Rideau Cottage, pending a review of work needed to repair 24 Sussex which was in poor condition.

Unlike 10 Downing Street or the White House, 24 Sussex Drive has been used almost exclusively as a place of residence (and therefore its address has never been widely used as a metonym for the Office of the Prime Minister). The prime minister's work is carried out by the Office of the Prime Minister in the Office of the Prime Minister and Privy Council building, near Parliament Hill. However, prime ministers have conducted some work at 24 Sussex Drive over the years, and informal meetings between prime ministers and other government or foreign officials have taken place in the house (foreign heads of state on state visits are officially hosted by the monarch or governor general at Rideau Hall).

Security at 24 Sussex was overhauled following an attempted assassination on November 5, 1995, by André Dallaire, who wandered around the house and grounds for nearly an hour before being confronted outside Jean Chrétien's bedroom by the Prime Minister's wife, Aline; she locked the door to the bedroom while Jean guarded it with an Inuit stone carving. Ultimately, Royal Canadian Mounted Police officers arrested Dallaire. Measures put in place after the incident included the addition of several more guards and security cameras to the house's attaché, and the installation of crash-proof barriers within the main gates.

Despite the building not having any bureaucratic function, it has been the location of protests, such as when farmers drove their tractors in a convoy past the front of the property in 2006 and when Greenpeace activists chained themselves to the front gates in March 2007.

Stephen Harper is the most recent prime minister to have resided at 24 Sussex Drive, leaving in 2015. 24 Sussex has remained unoccupied, but staff use its kitchen to prepare meals which are then delivered to Trudeau's family at Rideau Cottage.

The residence at 24 Sussex Drive is a large, limestone-clad structure set on 1.6 hectares (4.0 acres) on the south bank of the Ottawa River, overlooking Governor Bay, next to the French embassy and opposite the main entrance to Rideau Hall. The house consists of 35 rooms spread on four floors, including the basement, connected by an elevator and many staircases. The basement consists of support rooms, while the main floor holds the dining room, living room, kitchen (which is staffed by a head chef and support staff), main stair hall, prime minister's library, and a sun room. The second floor is primarily bedrooms, including the master bedroom, as well as a family room (described by Margaret Trudeau as her "freedom room") and the office of prime minister's spouse. The third floor contains additional bedrooms and a private study for the prime minister.

The exterior of the house is a mid-century modern take on Norman Revival architecture. When originally built, it was very much of the Victorian (Queen Anne) style; it had high gables, extensive verandahs, and a liberal use of gingerbread trim. A turret was added by the Edwards family in 1907. After it was decided in 1950 the house would become the official residence of the prime minister, the turret, widow's walk, trim, main gable at the front, verandahs, and porte-cochère were removed and an extension added to the east. The interior was gutted, save for part of the dining room.

The National Capital Commission (NCC) maintains the house, its property, and a selection of historic furnishings from the Crown Collection for use in the public rooms of the mansion, ranging from musical instruments to chairs, tables, and paintings by famous Canadians. However, due to the lack of restraints on the prime minister of the day to do what he or she pleases with the home, several have left their own marks on the building. For example, the rear patio was enclosed and winterized while Lester B. Pearson was prime minister and inside, Pearson's wife, Maryon, created in the basement the Canadiana Room, where she collected Canadian antiques and craft-work. While Joe Clark and his family were resident at 24 Sussex, the interiors were redecorated, the dining room ceiling receiving gold leaf re-purposed from another project. Unnamed business associates of Pierre Trudeau installed a swimming pool for his frequent workouts. The pool, designed by government architect Stig Harvor, reportedly cost $275,000 due to an underground access increasing the expense. This was raised in a "public fund" headed by Keith Davey, the donors to which were never made public. Brian Mulroney was the first prime minister to have the costs of renovations publicly revealed. The high tab for his and his wife's alterations to the building caused political controversy, especially as some of the costs were paid for from the PC Canada Fund, which raised money from individual donations to fund the Progressive Conservative Party.

Since the renovation of the house in 2001, very little has been spent on upkeep of 24 Sussex Drive, leaving parts of it worn and outdated, including the heating and cooling systems, wiring, and roofing. On May 6, 2008, the Auditor General reported that the house was in poor condition and needed about $10 million in repairs and upgrades, which would require at least 12 to 15 months of "full access" to complete. In October 2015, Bryan Baeumler estimated $15 million might be necessary to properly renovate the residence. The NCC devised a plan for major renovations, asserting such a project would require approximately 18 months. In 2021 the NCC released a new cost estimate of $36.6 million to bring the house to a state of good repair. However, the estimate includes a 370-square-metre (4,000 sq ft) expansion of the main building to improve universal accessibility, functionality, and livability.

As of 2023, the building was infested with rodents, and "the walls, attic and basement are filled with carcasses and excrement". In May 2023, work began to strip the property of asbestos and to remove "obsolete mechanical, heating, and electrical systems" which were the reasons that the building was deemed a fire hazard. The NCC estimated that the work would take one year to complete.