Great Ardra, also known by numerous variant spellings, was a West African kingdom formerly located on the Slave Coast in what is now southern Benin. It was named for its capital, the modern Allada, which was also the main city and major port of the realm.
The city and kingdom were supposedly founded by a group of Aja migrants in the 12th or 13th century. Its kings "ruled with the consent of the elders of the people". The state reached the peak of its power in the 16th and early 17th centuries, when it was an important source of slaves for the Atlantic trade. In the mid-16th century, it had a population of about 30,000 people.
The name is variously spelled Ardra, Ardrah,Ardres, Hardre, Arda, Arada, and Arrada. It is also sometimes known by its capital's present-day name Allada.
According to the Fon oral tradition, the Aja settlers that established themselves in the area of present-day Allada arrived in southern Benin around the 12th or 13th centuries coming from Tado, on the Mono River. They established themselves in the area that currently corresponds to southern Benin, until circa 1600, when three brothers - Kokpon, Do-Aklin, and Te-Agdanlin - split the rule of the region amongst themselves: Kokpon took the capital city of Great Ardra, reigning over the Allada Kingdom, while his brother Do-Aklin founded Abomey (which would become capital of the Kingdom of Dahomey) and their brother Te-Agdanlin founded Little Ardra, also known as Ajatche, later called Porto Novo (literally, "New Port") by Portuguese traders (which is the current capital city of Benin).
Founded by Aja settlers, the settlement of Allada was in 1600 the most prominent of Aja states, bordering the nearby Oyo kingdom, to which the King of Allada was vassal and tributary. Although it was an inland kingdom, Allada maintained control of some sea ports such as Offra, Jaquin and Whydah, thus making Allada important in the growing slave trade business, which also granted Allada the economic means to pay its duties to Oyo.