Roman Catholic Chapel of St Mary

The Roman Catholic Chapel of St Mary is a private chapel located at Lulworth Castle, built between 1786 and 1787 for Thomas Weld, with John Tasker as the architect and builder. The chapel features ashlar stone walls and a flat roof topped with a shallow lead-covered dome at the center. It has a square plan with segmental apses on all four sides and a rectangular narthex at the south end, which is the liturgical "east" end. There are entrances at both the south and north sides, and the building is designed in a classical style.

The walls rest on a rusticated plinth and are topped with a parapet that has a moulded cornice. Carved urns are positioned at the angles of the central section. The windows, which have glazing bars, are arranged over two storeys to light the galleries. The south front features a central door with a fanlight set in a round-headed opening, sheltered by a shallow portico supported by Tuscan columns and an entablature. On either side of the door are niches with carved urns and a window above each.

Inside, the central area is defined by Tuscan columns, and the dome has a painted ceiling. The chapel contains a carved marble altar, a marble vase font, hatchments, and an organ, all dating from the 18th century. This chapel is noted as an early Post-Emancipation Roman Catholic church, and building accounts are held in the County Record Office.