The 1904–1905 Welsh Revival was the largest Christian revival in Wales during the 20th century. While by no means the best known of revivals, it was one of the most dramatic in terms of its effect on the population, and triggered revivals in several other countries. "The movement kept the churches of Wales filled for many years to come, seats being placed in the aisles in Mount Pleasant Baptist Church in Swansea for twenty years or so, for example. Meanwhile, the Awakening swept the rest of Britain, Scandinavia, parts of Europe, North America, the mission fields of India and the Orient, Africa and Latin America."
The last previous revival in Wales was in 1859, but this followed other developments. From 1850 onwards Christianity in Wales was markedly less Calvinistic in form. A generation of powerful biblical preachers ended, as leaders such as Christmas Evans (1766–1838), John Elias (1744–1841) and Henry Rees (1798–1869).
Between 1859 and 1904, there were local revivals in Cwmafan (1866), Rhondda (1879), Carmarthen and Blaenau Ffestiniog (1887), Dowlais (1890) and Pontnewydd (1892).
There is no clear origin for the movement but several locations can be viewed as major centres of the revival.
A prominent leader of the Revival was the Methodist preacher of New Quay, Joseph Jenkins, who arranged a conference in New Quay in 1903 with the theme "to deepen our loyalty to Christ". After a meeting in February 1904, the regular Sunday meetings as well as the newly founded midweek meetings became lively and members of Joseph Jenkins' church went to other nearby towns and villages to 'witness' to the effects of how accepting Christ's message had influenced their lives.