The Church of the Holy Trinity, Westport was built on a site donated to the parishioners on 23 December 1868 by the Most Noble George John, Third Marquess of Sligo, who also provided almost all the funds for erecting and adorning the church. This church replaced the old parish church built in 1797 that now lies in ruins beside the Carrowbeg River in the demesne of Westport House.

Holy Trinity is said to be the last church built before the disestablishment of the Church of Ireland in 1871. It was built with the assistance of the Ecclesiastical Commissioners. There was also a local subscription list and the work is estimated to have cost over £ 80,000. The consecration of the church took place on 26 September 1872 and the consecrating bishop was almost certainly the Hon. and Right Reverend Charles Broderick Bernard, Bishop of Tuam.

From an architectural point of view it can be noted that the church incorporates a "hammer" roof and a very fine "pencil’ spire which rises to 100 feet in height and is capped with a cross which is twelve feet high. The stone carving is attributed to Charles Harrison and it is very involved work done on Portland stone. The intricacy of the work can be easily noted on the tower door and on the surrounds of the windows. The interior of the church reflects the influence of the mid eighteenth and nineteenth centuries. The marble of the spacious sanctuary is from Carrara, and the mosaics and murals were the work of craftsmen from Italy. The murals, which are mostly scenes from the Gospels, are said by some to have been copied from St. Peter’s in Rome. Others say that they are reminiscent of the floor of Siena Cathedral, Italy. The texture of the murals is marble, overlaid with gold leaf in places. The designs are traced out in marble, and filled with black cement. The best known of the murals is the depiction of Leonardo da Vinci’s The Last Supper over the main door at the West End of the church. The pulpit can safely be described as one of the most beautiful in Ireland and is carved in alabaster. It is reported that this alabaster was part of a cargo of a ship that was wrecked in Clew Bay and washed up on the lands of the Sligo Estate. The organ was moved to Holy Trinity Church from the old parish church in the demesne. It is dated 1852.

Apart from the richness of decoration in the mosaics and murals the church is also endowed with fine stained glass windows. Perhaps the most beautiful is the very perfect "rose" window at the west end of the building. There are also four windows on the south wall. The first is in memory of the Third Marquess of Sligo; the second is in memory of the Livingstone family; the third is in memory of Catherine McIllree and the fourth is in memory of Wilson-Lowen. There are three windows on the north wall. The first of these was erected by the six Livingstone sons to their parents; the second is in memory of Hester Catherine, wife of the second Marquess and the third is in memory of Lieutenant Edward David Kelly R.H.A., whose features are said to be those of the disciple in the boat with our Lord. The two small windows near the organ, depicting St. George and St. Patrick, came in recent years from Belclare Church.

Canon James Owen Hannay (whose nom de plume was George A Bermingham) was rector of the parish from 1892 to 1913. He was famous for his voluminous literary attainments and was a loyal supporter of Dr. Douglas Hyde and the Gaelic League.

Canon Hannay described the church as "a church which it is easy to love, beautifully decorated and rich in modern carving". Many a visitor would be happy to agree with such sentiments.

By Brian Hoban