County Mayo on Wikipedia.

Achill Sound (on Achill Island), Sisters of Mercy (R.C.). © Bill Henderson.

Ballintubber (also Ballintober), the Abbey (R.C.). © Len Brankin. Link1. Link2.
Bohola, Church of the Immaculate Conception and St. Joseph Bohola (R.C.). © Bill Henderson.

Bunnacurry, St. Joseph. (R.C.). © Bill Henderson.

Cong.

Crossmolina, St. Mary (CoI). © Bill Henderson.

Finney, Immaculate Conception (R.C.). © Len Brankin.
Foxford, St. Mary & St. Michael (R.C.). Church of Ireland. © Bill Henderson.

Glencorrib, Church of the Immaculate Conception (R.C.). © Bill Henderson.

Glenhest, St. Joseph. (R.C.). © Bill Henderson.

Kildonnet (on Achill Island), ruins of the old R.C. church. © Bill Henderson.

Kiltamagh, St. Joseph. (R.C.). © Bill Henderson.

Knock, the Roman Catholic Basilica. St. Joseph at the Shrine. (R.C.). © Bill Henderson. Just visible behind St. Joseph is the old church still in use. © Graeme Harvey.

Louisburg, St. Patrick (R.C.). © Bill Henderson.

Mulranny, Catholic Church. © Bill Henderson.

Newport, St. Patrick (R.C.). © Bill Henderson.

Partry, St. Mary (R.C.). © Len Brankin.
Pollagh, St. Patrick (R.C.). © Bill Henderson.

Shanvaghera, St Anne (R.C.). © Graeme Harvey.

Straide, Catholic Church. © Bill Henderson.

Swinford, Church of Our Lady (R.C.). © Bill Henderson.

Turlough, Church of Ireland. © Bill Henderson.

Westport, St. Mary (R.C.). Holy Trinity (CoI). © Bill Henderson.