Downtown Ottawa is the central area of Ottawa, Ontario, Canada. It is sometimes referred to as the Central Business District and contains Ottawa's financial district. It is bordered by the Ottawa River to the north, the Rideau Canal to the east, Gloucester Street to the south and Bronson Avenue to the west. This area and the residential neighbourhood to the south are also known locally as 'Centretown'. The total population of the area is 5,501 (2021 Census).

Downtown Ottawa is dominated by government buildings, including Parliament Hill and the Supreme Court. Most prominent buildings are situated along Wellington, Sparks and Elgin streets. Most of the buildings are office towers containing the various government departments. While most of Ottawa's high tech industry is based elsewhere it also has a significant presence in the downtown core. The downtown also contains a number of apartments, hotels, and condominiums as well as the older single family homes and townhouses along its edges.

From Wellington to Laurier, Elgin Street is the site of several landmarks, the Château Laurier, the National Arts Centre, Lord Elgin Hotel, Place Bell Canada, the Ottawa Courthouse, and Ottawa City Hall. Other prominent buildings include World Exchange Plaza office and retail complex, encompassing a whole city block on the south-west corner of Queen and Metcalfe, featuring the 'clock ball' on top, and Place de Ville, a complex incorporating four office buildings and two large hotels on two city blocks, with all buildings interconnected through an underground retail concourse. There are also many prominent heritage buildings along Sparks Street.

The towers of downtown Ottawa are not as tall as those in other cities, as legislation prevented buildings being built taller than 150 feet until the 1960s, so as not to overshadow the Parliament Buildings and the Peace Tower (similar to Washington, D.C.'s Heights of Buildings Act). Today, several buildings are taller than the Peace Tower, with the tallest being the 29-storey Place de Ville (Tower C) at 112 m (367 ft), which was built above the height limit, and several hotels being slightly shorter but with 30-35 stories.

The downtown employs about 100,000 people and currently holds around 20 million square feet (1.9 million square metres) of office space.

East of the canal, but west of King Edward Avenue, including the Rideau Centre and the ByWard Market, is also normally considered downtown, and is referred to locally as 'Lowertown' or Lower Town. The residential neighbourhoods around the central business district are also generally referred to as being downtown.

These include Centretown to the south and Sandy Hill and Lower Town to the east. North of the Ottawa River the centre of Gatineau, Quebec, can be considered an extension of Ottawa's downtown.

According to the 2016 Canadian census. Area defined as the part of Ottawa north of Gloucester Street, east of Bronson, south of the Ottawa River and west of the Rideau Canal.