Addedomarus (sometimes written Aθθedomarus on coins) was a king of south-eastern Britain in the late 1st century BC. His name is known only from his inscribed coins, the distribution of which seem to indicate that he was the ruler of the Trinovantes.
He was the first king to produce inscribed coins north of the Thames, perhaps as early as 35 BC, although some estimates are as late as 15 BC. He seems to have moved the Trinovantian capital from Braughing in Hertfordshire to Camulodunum (Colchester, Essex). For a brief period (ca. 15-10 BC) he seems to have been supplanted by Tasciovanus of the Catuvellauni, who issued coins from Camulodunum at that time. Addedomarus then appears to have regained power and reigned until 10-5 BC, when he was succeeded by Dubnovellaunus.
Addedomarus appears in later, post-Roman and medieval British Celtic genealogies and legends as Aedd Mawr (Addedo the Great). The Welsh Triads recall Aedd Mawr as one of the founders of Britain.
Philip de Jersey, Celtic Coinage in Britain, Shire Archaeology, 1996, ISBN 0-7478-0325-0