Fonseca Guimaraens is one of the most well known port producers located in Vila Nova de Gaia, Portugal. It was originally founded in the 1600s as Fonseca, Moneteiro & Company. The Fonseca family conducted trade in wine, foodstuffs, olive oil and cloth primarily with Brazil in exchange for sugar cane, hemp and snuff from the colonies. By the year 1820, the Fonsecas primary trade was in port wine. In 1822 Manuel Pedro Guimaraens acquired the majority of the Fonseca holdings. The selling Fonsecas stipulated that their name be retained both as a brand name, and a family name for whoever should own the business. In 1948, the company was purchased by the Yeatman family, who own Taylor, Fladgate and Yeatman, another of the big Oporto port houses.

Fonseca and its sister Taylor Fladgate are considered to be among the top port houses in all of Portugal, along with W & J Graham's, Smith Woodhouse, Dow's, Warres and Croft.

Fonseca product include the premium reserve Fonseca Bin No. 27, Siroco White Port, 10, 20, 30 and 40-year tawny ports, various late bottled vintage ports and their classic vintage ports.

See also: 1977 Fonseca Vintage Port.