Rothesay (/ˈrɒ(θ)seɪ/) is a suburban town located in Kings County, New Brunswick, Canada. Located within Saint John's metropolitan area, it borders the town of Quispamsis to form the Kennebecasis Valley and is located along the lower Kennebecasis River. As of 2021, the population of Rothesay was 11,977.

Located along the lower Kennebecasis River valley, Rothesay borders the city of Saint John to the southwest, and the neighbouring town of Quispamsis to the northeast. It is served by a secondary mainline of the Canadian National Railway, though there is no longer any passenger service on the line.

The town of Rothesay developed first as a shipbuilding centre and later as a summer home community for Saint John's wealthy elite with the arrival of the European and North American Railway in 1853. There is a commonly known story that the new town was named in honour of the visiting Prince of Wales, later King Edward VII, in 1860 because the area was said to have reminded him of Rothesay, on the Isle of Bute, in Scotland.

However, an entry made in the diary of William Franklin Bunting, of Saint John, during the same visit refers to the Rothesay train station. It is unlikely that the name would have taken hold less than a day after the prince's passage through the settlement and so it likely predates the visit or was specifically bestowed on the town in the prince's honour as Duke of Rothesay. In 1870, a Saint John-owned ship named Rothesay made a famous voyage when a 20-year-old woman named Bessie Hall took command of the fever-stricken ship and sailed it from Florida to Liverpool, England.

Many historical landmarks are located in the town of Rothesay, such as the Rothesay Common, the Rothesay Yacht Club, the former train station (one of the last remaining examples of early railway architecture in Canada), many homes that pre-date Confederation, public parks and modern amenities. The community provides numerous places of worship and recreation, along with the convenience of local retail and large-scale commercial developments in the nearby city of Saint John. Police services are provided by Kennebecasis Regional Police Force.

Rothesay lies in the Anglophone South School District. Schools include Rothesay Park School, Rothesay High School, Rothesay Netherwood School, and Fairvale Elementary School. Rothesay was formerly the headquarters of New Brunswick School District 06; both New Brunswick Route 100 and New Brunswick Route 111 run through the town and connect with New Brunswick Route 1. The city is served by Saint John Transit.

In the 2021 Census of Population conducted by Statistics Canada, Rothesay had a population of 11,977 living in 4,873 of its 5,007 total private dwellings, a change of 2.7% from its 2016 population of 11,659. With a land area of 34.59 km² (13.36 sq mi), it had a population density of 346.3/km² (896.8/sq mi) in 2021.

Following the December 1992 release of a government discussion paper entitled "Strengthening Municipal Government in New Brunswick's Urban Centres", a series of localized feasibility studies were commissioned by the Frank McKenna Liberals targeting six geographic areas: Edmunston, Campbellton, Dalhousie, Miramichi, Moncton, and Saint John. In each instance, a panel composed of local representatives and expert consulting staff made specific recommendations for each urban-centred region. The report for the Greater Saint John area, "A Community of Communities: Creating a stronger future" - often referred to simply as the Cormier Report - offered two potential solutions to the Province for consolidating the many municipalities in Greater Saint John, neither of which was ultimately adopted by government.