Fréjus Cathedral (Cathédrale Saint-Léonce de Fréjus) is a Roman Catholic cathedral, and a national monument of France, situated in the town of Fréjus in the Var department of Provence, in southeast France.

The cathedral was the seat of the Bishop of Fréjus, although from 1751 the bishops resided in Draguignan. The see was abolished in 1801 but restored under the Concordat of 1817. In 1957 the see was united with that of Toulon to form the present Diocese of Fréjus-Toulon, with its seat at Toulon Cathedral.

It is part of a complex of medieval religious buildings dating from between the 5th and 13th centuries, when Fréjus was an important religious and commercial centre of Provence, comprising a parish church and a cathedral under one roof; a baptistery; the bishop's residence; a canonry, for the community of priests who served under the bishop; and a cloister.

The baptistery of the cathedral, built in the 5th century but hidden during later reconstruction, was rediscovered in 1925. It is considered the oldest Christian structure in Provence, and one of the oldest in France.