Gananoque (/ˌɡænəˈnɒkweɪ/ GAN-ə-NOK-way) is a town in the United Counties of Leeds and Grenville of Ontario, Canada. The town had a population of 5,383 year-round residents in the 2021 Canadian Census, as well as summer residents sometimes referred to as "Islanders" because of the Thousand Islands in the St. Lawrence River, Gananoque's most important tourist attraction. The Gananoque River flows through the town and the St. Lawrence River serves as the southern boundary of the town.

The name "Gananoque", first given to the river, is of indigenous origin, but its roots and meaning are unclear. Over the centuries, it has been written in no less than 57 different variations, making it difficult to determine its meaning.

Among the possible meanings proposed are:

The Mohawk-English Dictionary of 1971 lists the name as Kananókwi or Kananóhkwih.

In 1784, the site was surveyed and land was granted to Loyalists John Johnson (on the east side of the Gananoque River) and Colonel Joel Stone (on the west side). Johnson did little to develop his possession, but Col Stone, who served with Loyalist militia during the American Revolutionary War, established a sawmill on this site in 1789. In 1812, Charles McDonald laid out the town site and also built a mill, its first store, and church there.

During the War of 1812, American forces raided the government depot in the town to disrupt the flow of British supplies between Kingston and Montreal. The raiders seized the supplies they found and burned the depot. Within a month of the raid, construction of the Gananoque Blockhouse was started, with completion in 1813. It had an octagonal log parapet containing five guns. The blockhouse was abandoned after the War of 1812 and given to a private landowner.

The blockhouse was quickly repaired in the 1837–38 Patriot War when there were fears American militia forces were planning to attack. The Gananoque Blockhouse stood until 1852.

In 1890, Gananoque was incorporated as a town.