The Setantii (sometimes read as Segantii) were a possible pre-Roman British people who apparently lived in the western and southern littoral of Lancashire in England. It is thought likely they were a sept or sub-tribe of the Brigantes, who, at the time of the Roman invasion, dominated much of what is now northern England.
The Setantii name is known from a single source only, the 2nd century Geographia of Ptolemy. Recorded there is the placename Portus Setantiorum (Port of the Setantii). Its precise location remains unknown although various suggestions have been made, including the possibility that it has since been lost to erosion. Also recorded by Ptolemy is the hydronym Seteia, assumed by its position in his text to refer to the River Mersey.
The name of the Setantii has been associated with the Irish hero Cúchulainn, whose birthname, Sétanta, bears clear similarities to it. The first Professor of Celtic at Oxford University, Sir John Rhys, also suggested an association between these two and Seithenyn, a Welsh character known from the Black Book of Carmarthen.
- "PORTVS SETANTIORVM: The Seaport of the Setantii". roman-britain.org. Retrieved 2016-07-17.
- N. Higham, The Northern Counties to AD 1000 Longman, Regional History of England Series, 1986
- Middleton, Wells, Huckerby, The Wetlands of North Lancashire (North West Wetlands Survey), University of Lancaster (1995)
- Buxton, K. M. & Howard-Davies C. L. E., Roman Forts in the Fylde. Excavations at Dowbridge Kirkham, Lancaster University of Lancaster (2000)
- Rhys, John (1901). Celtic Folklore: Welsh and Manx (2004 reprint). University Press of the Pacific. Chapter VI: The Folklore of the Wells. ISBN 1-4102-1519-9.