The Cathedral of St Louis (Bulgarian: катедрала „Свети Лудвиг“, katedrala „Sveti Ludvig“) is a Roman Catholic cathedral in the city of Plovdiv, Bulgaria. Co-cathedral of the Diocese of Sofia and Plovdiv together with the Cathedral of St Joseph in Sofia, it is one of the largest and most important Roman Catholic places of worship in the country. It was named after Louis IX of France, commonly known as "Saint Louis".