Carrick-on-Shannon ("weir of the marshy ridge") is the county town of County Leitrim in Ireland. It is the largest town in the county of Leitrim and the smallest county town in the entire country. A smaller part of the town lies in County Roscommon. The population of the town was 4,062 in 2016. It is situated on a strategic crossing point of the River Shannon. The Leitrim part of the town is in the civil parish of Kiltoghert which is in the ancient barony of Leitrim.

Until the early 19th century, the head of the Shannon Navigation was Drumsna. In the 1840s the improvement of the navigation entailed extensive dredging of the river, the cutting of Jamestown Canal, the construction of locks at Drumsna and Knockvicar, and the building of a new bridge and Quays at Carrick-on-Shannon. The new bridge, built in 1846, took the place of a nine arch stone bridge, which in turn replaced a wooden structure.

For over a century, until the closing of the Grand Canal Company in 1960, Carrick was a major depot for river trade; timber, cement, hardware, and especially Guinness stout were all transported here from Dublin, Athlone, and Limerick.