St. Denys of Paris is a Christian martyr and the patron saint of France. He is believed to have been the first bishop of Paris and is often depicted holding his own head, symbolizing his martyrdom. According to tradition, he was executed around the year 250 AD during the persecution of Christians under the Roman Emperor Decius. His feast day is celebrated on October 9th, and he is venerated in various Christian denominations. St. Denys is also associated with the Sainte-Chapelle and the Basilica of Saint-Denis, where many French kings are buried, highlighting his significance in French history and culture.