The black and white flag of Cornwall's patron saint flew prominently from buildings across the county on Friday.
Hundreds of people took part in marches, including one through the streets of Truro to the cathedral, to mark the annual St Piran's Day.
There will also be a trek across the sand dunes at Perranporth on Sunday.
It was there St Piran is said to have come ashore in the sixth Century, having made the journey from Ireland in a currach.
A replica currach, made using traditional methods, is being used as part of this year's celebrations.
Chris Roynan, who teaches at Porthleven Junior School, took his class on one of the marches.
"It has been brilliant and this is very important for us all," he said.
"We all feel very proud of Cornwall's culture and heritage and this is a great chance to celebrate that."