Saint Duthac (or Duthus or Duthak) (1000–1065) is the patron saint of Tain in Scotland.
According to the Breviary of Aberdeen, Duthac was a native Scot. Tradition has it that Duthac was educated in Ireland and died in Tain.
A chapel was built in his honor and a sanctuary established at Tain. The great Ferchar mac in tSagairt, first Earl or Mormaer of Ross in the thirteenth century, and was ministered by the Norbertine canons of Fearn Abbey. A century later, this sanctuary was notably breached by English supporters who captured Robert the Bruce's wife and daughter sheltering in the chapel. The chapel was burnt later in political violence between regional power groups, namely the Clan MacKay and the Clan Ross. The ruins of the chapel still exist as a centrepiece of a cemetery along the shores of the Dornoch Firth.
Saint Duthac was greatly venerated in Scotland before the (First) Reformation - Celtic to Catholic - and his memory is still preserved in place names, notably Kilduthie; Arduthie near Stonehaven and Kilduich on the Loch Duich. Tain, where he died and was buried, had the Church built specially in his honour. His death is recorded in "The Annals of Ulster" for the year 1065. After many years his body was found to be incorrupt and his relics were translated to a more splendid shrine at St. Duthus Collegiate Church built between 1370 and 1458. They disappeared in 1560 at the time of the Reformation.
He was known as the Chief Confessor of Ireland and Scotland (Dubtach Albanach) and his saint's feast day is 8 March. His shrine was visited by King James IV, Robert the Bruce and his family, plus many other notables.
Tain was called Baile Dhubhthaich in Scottish Gaelic or Duthac's Town and near it stands St. Duthac's Cairn, although the biennial Fairs called by his name are no longer held in the town.