County Donegal on Wikipedia.

Ardara, Methodist Church. © Graeme Harvey.

Ballintra, St. Brigid (R.C.). Link. Drumholm Parish Church (CoI). Methodist Church. All © Graeme Harvey.
Ballybrack, St. Mary. From an old postcard in Reg Dosell's Collection. Although the postcard gives the location as Moville (under which this entry was previously listed), Ben Palmer has advised that the present Parish Church is St. Pius, built in 1953 in Moville town centre. The old parish church is St. Mary, a couple of miles away in Ballybrack, which is still commonly used for marriages and burials. A modern view. © Ben Palmer.
Ballyshannon, St. Patrick (R.C.). Another view. Both © Graeme Harvey. An old postcard view, from Reg Dosell's Collection. Interior view, © Joseph Cantwell. Killbarron Parish Church (CoI). © Graeme Harvey. Former Presbyterian Church - services ceased in 2007. G 873 615. © Gerard Close. St. Joseph (R.C.), known locally as St. Josephs the Rock. G 871 611. © Gerard Close.
Bridgetown, Gospel Hall. © Graeme Harvey.
Bruckless, St. Conall and St. Joseph (R.C.). © Graeme Harvey.
Bundoran, Finner Parish Church (CoI). The former Presbyterian Church. Both © Graeme Harvey. Church of The Immaculate Conception (R.C.). G 821 585. © Gerard Close. Former Methodist Church, now a coffee shop. G 821 591. © Gerard Close. Since the previous photo was taken, the Catholic church has been refurbished, and re-dedicated as Our Lady Star of the Sea. © Gerard Close (2011).

Carrickfinn. © Lorraine Waddington.
Carrigart, St. John the Baptist (R.C., 1886). C 130 366. © Gerard Close (2014).
Castlefin, St. Mary (R.C.). © Graeme Harvey.
Clar, St. Agatha (R.C.). © Graeme Harvey.

Donegal.

Greencastle, St. Finian (CoI, 1738). © Ben Palmer (2006).
Gweedore. © Lorraine Waddington.

Killaghtee, St. Peter (CoI). © Graeme Harvey.
Killybegs, St. Mary. © Graeme Harvey.
Kilmacrenan, St. Finian and St. Mark (CoI). C 140 204. © Gerard Close (2014).
Killymard, St. Mary (R.C.). G 931 802. The old church stands opposite. Both © Gerard Close (2011).

Laghey, the Parish Church (CoI). © Graeme Harvey.
Letterkenny, St. Eunan's Cathedral (R.C.). © Graeme Harvey. An old postcard view, from Reg Dosell's Collection. Link. Trinity Presbyterian Church. © Graeme Harvey. Link. Conwal Parish Church (CoI). © Graeme Harvey. Link.
Lifford, Church of Slugadius (CoI). © Graeme Harvey.
Liscooley, Donoughmore Presbyterian Church. © Graeme Harvey.
Lough Derg, Basilica of St. Patrick (1930). A place of pilgrimage for over 1500 years, photography is not allowed on the island, so this was taken from the opposite shore. H 083 733. Link. For those unable to make the journey across to the island, St. Brigid's Chapel of Ease was built. J 090 732. Both © Gerard Close (2013).
Lough Eske, Christ Church (CoI). © Graeme Harvey.

Moville, St. Pius X (R.C., 1953). © Ben Palmer (2006). Link1. Link2.

Pettigo, Catholic Church. Templecarne Parish Church (CoI). Both © Graeme Harvey.

Rossnowlagh, Church of the Immaculate Heart of Mary (R.C.) at the Franciscan Friary. G 866 673. Presbyterian Church (1906). G 878 672. Gerry had advised that this was the only Tin Church still in use in Ireland, but Adam McCurdy has been in touch to say that there is at least one other in Rearcross, Co. Tipperary (see here). Liam Kenny has advised of another at Sallins, Co. Kildate (see here). St. John (CoI). G 909 696. All © Gerard Close. The remains of St. Barran (15th century). G 857 660. © Gerard Close (2013).

Shrove, St. Joseph (R.C.,1947). Both © Ben Palmer (2006). Link1. Link2.
Stranorlar.

Termon, St. Columba (R.C., 1854). C 116 223. © Gerard Close (2014).

Urney, Christ Church (CoI). © Graeme Harvey.