Demerara (Dutch: Demerary) was a region in South America in what is now Guyana that was colonised by the Dutch in 1611. The British invaded and captured the area in 1796. It was located about the lower courses of the Demerara River, and its main town was Georgetown.

Demerara sugar is so named because originally it came from sugar cane fields in the colony of Demerara.

In 1781 the American revolution induced the Dutch Republic to join with the Bourbon side against the British, a large fleet under Admiral Lord Rodney's was sent to the West Indies, and after having made some seizures in the Caribbean Islands, a squadron was detached to take possession of the colonies of Essequebo and Demerara, which was accomplished without much difficulty. In 1782 the French took possession of the whole Dutch settlements compelling Gov. Robert Kinston to surrender. The peace of Paris, which occurred in 1783 restored these territories to the Dutch.

The British returned the colony to the Dutch in 1802 under the terms of the Peace of Amiens, but re-took control of it a year later. On 13 August 1814 the British combined the colonies of Demerara and Essequibo into the colony of Demerara-Essequibo. On 20 November 1815 the colony was formally ceded to Britain by the Netherlands. On 21 July 1831 Demerara-Essequibo united with Berbice as British Guiana, now Guyana. Demerara is now one of the three counties of Guyana, the other two being Berbice and Essequibo.