Ginger, auburn, strawberry blonde - all types of redheads turned out in their hundreds for concerts and fashion shows in the western French town.
Many participants shared stories of how being teased with jibes like "Carrot-top" during their childhood.
Among the best-selling items on display were T-shirts emblazoned with the slogan "Ginger is the new black".
The biggest get-together of redheads in the world takes place every year in the Netherlands.
By midday, 1,200 people had showed up, said organiser Pascal Sacleux, who expressed the hope that "one day the jokes at the expense of redheads will be a thing of the past, when everyone realises how unfounded and stupid they are".
Brittany has a larger proportion of redheads than the rest of France.
It was named after Celtic Britonic speakers, who emigrated from south-west England from the third to the ninth century of the common era, mostly at the time of the Anglo-Saxon invasion of Britain.