Baptist
Ainon is a Welsh Baptist Chapel and had its origins in a group of baptists who began meeting in a house in nearby Pelican Street. Ainon Chapel was first constructed in 1848, and was rebuilt in 1888. It is located on Heol Giedd, the other side of the river from what is now the main town of Ystradgynlais, but what in the past used to be more the heart of the old town.

English Baptist
As a legal entity, Bethany English Baptist Church was founded in 1902, first meeting at Ainon Chapel, then at the ILP Hall (later Elim Hall), before building their first wood-and-iron chapel in 1921. They purchased Brynawel Chapel in 1946, renaming it to Bethany Chapel, and closed in 1990, with the chapel being demolished and replaced by a private house.

Independent
Brynawel Chapel was a Welsh Congregational Chapel, constructed on Brecon Road in 1911. It was one of several in the town viewed as being a daughter church to Sardis. It was sold to Bethany Chapel in 1946.

Baptist
Calfaria was a Welsh baptist chapel in Station Road, Ystradgynlais, constructed in 1913. It closed in 2014 when the premises were purchased by Roger Castle & Daughter Funeral Directors.

Spiritualist
DATA

Denomination
Elim Hall was an offshoot of the Elim Free Mission, who were associated with the apostolics and with the sending of missionaries overseas. They appear to have taken over the old I.L.P. Hall in Ysradgynlais, certainly by 1926, and continued to be in action through to at least the 1950s.

Congregational
The English Congregational Church in Ystradgynlais was built in 1907 and brought into a joint pastorate with the English Congregational Church, Ystalyfera in 1931. It closed and was sold to a local business who use it as a storeroom.

Roman Catholic
Construction of Sacred Heart began in May 1938 and it was officially opened on 22nd January 1939. In 1944, the Salvatorian Fathers took over the running of the church. It remains active and still going strong in the 21st century.

Independent
Sardis Independent Chapel was built in 1861 and was still going strong in the early 2010s, but has since closed and been put up for sale. It remains in existence as a legal entity, using the vestry, now spun off as a building its own right, as the venue for services and other activities.

Apostolic
Saron Apostolic Church, Ystradgynlais, was constructed on Ynyscedwyn Road in 1927 and rebuilt in 1990, and it is now known as Church in the Community (CITC).

Anglican
Saint Cynog's Church, Ystradgynlais, is of medieval foundation, though the current building dates to 1861. Previously associated with it was the Old Church Institute used a venue for events, but this was gradually superceded with the construction of the church hall on Pantyffynon Road in 1935. Recent changes have seen a ministry area created consisting of St Cynog's, St David's, Ystalyfera and the churches at Callwen and Coelbren.

Methodist
Tabernacl Ystradgynlais began as an offshoot of Yorath Chapel, Cwmgiedd in order to deal with the growing population of the area. While it was being constructed, the congregation met in what had been a private house in Gough Buildings (now Rhestr Fawr) and was then styled as Adulam Vestry, neighbouring The Star public house. Adulam Vestry was able to register births, and remained open for a short while after Tabernacl got going.