St Tanwg’s Church was built in 1840 and dedicated to St Tanwg, one of the Breton Saints of the 5th century who accompanied Cadfan on his early mission to Bardsey Island. Prior to the building of this church, the church on the shore of Llandanwg, a mile south of Harlech, was the Parish Church. The fifteenth century font from the old church now stands in the ‘Children’s Corner’ of this church.

About the turn of the century strenuous efforts were made to make St Tanwg’s a worthy parish church. The chancel and the organ chamber were added. One of the gems of the church is its Father Willis organ. Originally this organ was a gift to St. David’s Church, Glanadda, Bangor, by Mrs. Symes of Gorphwyafa in 1898, however after only a few years of use they found it not large enough for the churches use, and St Tanwg’s was able to acquire it around 1903. A lot of time and money has been spent on this organ over the past few years, and it has recently been restored.
The lectern was a gift from the Earl of Winchelsea, Bron-y-graig, a family of importance in Harlech for many years.

The ‘Children’s Corner’ was a gift of Mrs Ruth Evans in memory of her son, Flying Officer Colin Griffiths who was killed in 1944. The Altar Rails in the Lady Chapel were the gift og Miss Agnes Beattie who was evacuated with her school from Birkenhead at the beginning of the last war.

The chairs in the Sanctuary and the Litany Desk were the gift of the Rev. R. Parker Jones on his retirement in 1945 and he and his wife gave the east windows in memory of their only son the Rev F.J. Parker Jones. He was a curate in Sidcup, Kent, and drowned in the river Medwy trying to save a young boy.

The Altar Rails and the Hanging cross were the gift of Mrs Marquand and Mrs. Rowe in thanksgiving for their evacuation to Harlech during the last war.

The kneeler at the Altar was made and donated by Lady Pamela Harlech, the wife of the late Lord Harlech who was tragically killed in a motor accident in 1985.

The Good Shepherd window was a gift from Mrs Parker Jones in memory of her husband who was Vicar of Harlech from 1915-1945.

In 1939 preparations were started to celebrate the centenary of the Church in 1940 but plans had to be cancelled when the Second World War broke out. replaced by chairs.

In 1961-1962 the church underwent a restoration during the incumbency of the Rev Meurig Foulkes. The choir stalls came from Bangor Cathedral, and the old worm infested box pews were removed.

The bell was made C. & G. Mears Foundry of London and was a gift of Col Le Clarc as a thank offering (as is incribed on the bell) “for the preservation of himself and family in attempting to cross the estuary of Treath Bach on 14th August 1844. D. Evans, Vicar, L. Foulkes and J. Thomas, Church Wardens.”