Cathedral of St Louis, Catholic cathedral in central Plovdiv, Bulgaria.

The Cathedral of St Louis is a Roman Catholic co-cathedral in Plovdiv, built between 1858 and 1861 by master builder Ivan Boyanin to a design by Italian architect Alfonso. Its facade combines Neoclassical and Neo-Baroque elements with statues, half-columns and decorative ornaments. A separate belfry in Florentine style, known as the Leontiana Tower, stands beside it.

Construction began in the 1850s under the direction of Vicar Andrea Canova, with the building opening to worshippers in 1861. This period marked an unusual moment for Catholic presence in a region under Ottoman control.

The cathedral's first organ, installed in 1861, was the first in Bulgaria; a 12-stop pipe organ replaced it in 1991. The parish also supported the Women's Charity Society "Holy Mother" from 1886 to 1950 and the Bulgarian Catholic Society "Petar Parchevich" from 1921 to 1946.

Visitors can enter during the week, though the building remains primarily a place of worship where services are held regularly. It is best to check opening times beforehand, as access may be limited during religious ceremonies.

Princess Marie Louise of Bourbon-Parma, first wife of Ferdinand I of Bulgaria, is buried inside the cathedral at the far end, to the right of the altar. An inscription in Bulgarian and Latin on her life can be read on both sides of the tomb.