Cathedral of the Annunciation of the Blessed Virgin Mary and St Nathy, Ballaghaderreen, Catholic cathedral in Ballaghaderreen, Ireland.

The Cathedral of the Annunciation of the Blessed Virgin Mary and St Nathy in Ballaghaderreen is a Gothic Revival church built of grey limestone, 45.72 metres long, 17.9 metres wide and 20.4 metres high. Its four-stage west tower with a spire rises 59.6 metres, added in 1912 by William H. Byrne. The interior has a single nave, and a baptismal font from around 1870 stands south of the west door.

Construction began in 1855 under the commission of Bishop Patrick Durcan, and the building was consecrated in November 1860. It was established to serve the Diocese of Achonry and represents a significant religious building project of the mid-19th century.

The cathedral bears the names of two religious figures: the Annunciation of the Blessed Virgin Mary and Saint Nathy, reflecting local ecclesiastical traditions. This dual naming connects two venerated saints in the region's spiritual life.

The cathedral stands on Cathedral Street in Ballaghaderreen, County Roscommon. It closed for about six months from 2017 for roof repairs, stone pointing, lighting and a heating upgrade, with Masses moved to the chapel of St Nathy's College. The interior has a single nave, so the whole length is visible from the west door; the baptismal font of around 1870 stands south of that door.

The 59.6-metre tower and spire, added in 1912 by William H. Byrne, dwarf the grey limestone body of the church, which is 45.72 metres long, 17.9 metres wide and 20.4 metres high. The contrast in scale is easy to notice from Cathedral Street.