MONMOUTH ST MARY, a priory church, was dedicated to St Mary the Virgin. It was founded in 1101 and became the parish church later in the 12th century. The three-stage tower dates from the 14th century. By 1730 the church was sai to be in a "ruinous and decayed" condition and significant repairs and rebuilding took place in 1736. The spire was added in 1743, but it was in the late 18th century that the church was completely re-built; only the tower and spire survived. There are two chapels, Lady Chapel and North Chapel, and a south aisle. A tile in the south chapel displays a Bohun swan (a swan in chains), which was the emblem of Mary de Bohun, mother of Henry V, who was born in the castle nearby.

St Mary's Churchyard was closed in 1851, and Monmouth Cemetery was created elsewhere after decayed human remains began surfacing, creating a health hazard and terrible odours.