The Kingdom of Aidhne was formed in c.171 CE. Their leader is given as Conall Caol, son of Aonghus mac Úmhór. Connall was killed at the Battle of Maigh Mucruimhe in 195 A.D., and his body brought back to Aidhne where it was interred at a leacht called Carn Connell (itself the site of a major battle some centuries later).
The earliest surviving list of leaders appears in the Baile Chuind (The Ecstasy of Conn) a late seventh century poem (c.665 CE) in which Conn of the Hundred Battles experiences a vision of the kings who will succeed him. Many of these kings appear to correspond with the kings of later traditions, although the order is different, and some of the kings cannot be identified. The last four kings following Snechta Fína (Fínsnechta Fledach) do not correspond with any of the kings in later lists. The poem is therefore presumed to have been written during his time, and the kings who follow him are presumed to be fictional.
With few exceptions, kings belong to Dál Cuinn (the Connachta and Uí Néill). Understood as a list of Kings of Tara, it is not considered to be inclusive. A number of well known kings from the Laigin, Érainn, Ulaid, and Cruthin, are missing. The chief rivals of Dál Cuinn at the time of Conn's supposed floruit were the Dáirine, alias Corcu Loígde, two of whom are listed, but whose overkingdom in the south of Aidhne collapsed in the 7th century. They would be replaced by the Eóganachta, who established the Kingdom of Aidhne c.701 CE, later to rival Tara.
Since 1171, the Kingdom of Aidhne has had a successful and thriving trading relationship with the Kingdom of Osraige. They also share the same distrust and sectarian rivalry with Imperia, which many trace back to border conflicts from 1701. The nation currently has a long standing policy of non-aignment, but it will certainly aid any nation that is armed against Imperia.