The Diocese of Port-Louis is a Latin Church ecclesiastical territory or diocese of the Catholic Church located in the city of Port Louis, the capital city of Mauritius.

Port Louis is the capital city of Mauritius. It is mainly located in the Port Louis District, with a small western part in the Black River District. Port Louis is the country's financial and political centre, and the most populous city. It is administered by the Municipal City Council of Port Louis. According to the 2018 census conducted by Statistics Mauritius, the population was 147,066.