Ottawa ( ˈɒtəwə (help·info) or sometimes /ˈɒtəwɑː/) is the capital of Canada and a municipality within the Province of Ontario. Located in the Ottawa Valley in the eastern portion of Southern Ontario, the city lies on the southern banks of the Ottawa River, a major waterway forming the local boundary between the Provinces of Ontario and Quebec. The 2006 Census recorded the population at over 812,000, making it the fourth largest municipality in the country and second largest in Ontario. Connected by several bridges to its Quebec neighbour, the City of Gatineau on the northern shores of the Ottawa River, the two cities had a combined 2006 population of over 1,130,000, making it the country's fourth largest metropolitan area.

Ottawa is governed by a 24-member city council consisting of 23 councillors each representing one ward and the mayor, currently Larry O'Brien, elected at-large. As a single tier municipality, Ottawa has responsibility for all municipal services, including fire, ambulance, police, parks, roads, sidewalks, public transit, drinking water, stormwater, sanitary sewage and solid waste.

There is no federal capital district in Canada. Although it does not constitute a separate administrative district, Ottawa is part of the federally designated National Capital Region (NCR), which encompasses Ottawa, Gatineau and surroundings areas having a population of over 1,451,000. The National Capital Commission is a federal crown corporation charged with the responsibility of plannng and managing the federal government's interests in the NCR.

As with other national capitals, the word "Ottawa" is also used to refer by metonymy to the country's federal government, especially as opposed to provincial or municipal authorities.