Saint Joseph's Oratory of Mount Royal (French: "Oratoire Saint-Joseph du Mont-Royal" ) is a Roman Catholic minor basilica and national shrine on Westmount Summit in Montreal, Quebec.
 It is Canada's largest church and the twenty-seventh largest church building in the world.
Matthias Church (Hungarian: "Mátyás-templom" ) is a Roman Catholic church located in Budapest, Hungary, in front of the Fisherman's Bastion at the heart of Buda's Castle District.
 According to church tradition, it was originally built in Romanesque style in 1015, although no archaeological remains exist.
 The current building was constructed in the florid late Gothic style in the second half of the 14th century and was extensively restored in the late 19th century.
 It was the second largest church of medieval Buda and the seventh largest church of the medieval Hungarian Kingdom.
First Baptist Church of Panama City, FL is the largest church in Bay County, FL.
 The megachurch is listed as the 220th largest church of the Southern Baptist Convention in the nation, and is located at 640 Grace Ave, in the downtown area.
 The senior pastor is Dr. Craig Conner, the senior associate pastor is Bill Sears, the associate pastor as well as the minister of music is Ken Brookins, and the minister of students is Shane Booker
St. Stephen's Basilica (Hungarian: "Szent István-bazilika" , ] ) is a Roman Catholic basilica in Budapest, Hungary.
 It is named in honour of Stephen, the first King of Hungary (c 975–1038), whose supposed right hand is housed in the reliquary.
 It was the sixth largest church building in Hungary before 1920.
 Since the renaming of the primatial see, it's the co-cathedral of the Roman Catholic Archdiocese of Esztergom-Budapest.
 Today, it is the third largest church building in present-day Hungary.
The Catholic Church in Australia is part of the worldwide Catholic Church under the spiritual and administrative leadership of the Holy See.
 The religion arrived in Australia with the First Fleet in 1788, and since the 1960s, has remained stable at around one quarter of the Australian population.
 In 2016, there were 5,439,268 Australian Catholics, representing 23% of the overall population, and the Church was the single largest non-government provider of education, health, community and aged care services.
 Australia has 32 dioceses and 1,363 parishes.
 It has more than 180 congregations of sisters, brothers and religious priests, working in diverse vocations ranging from education, to health care, poverty alleviation, social justice, and cloistered contemplation.
 The Australian Catholic Bishops Conference is headed by the Archbishop of Melbourne, Denis Hart, and there is one living Australian cardinal: the current Prefect of the Secretariat for the Economy, George Pell.
 One Australian has been recognised as a saint by the Catholic Church: Mary MacKillop, who co-founded the Josephite religious institute of sisters in the 19th century.
St. Simon & St. Jude Church, known colloquially as Tignish Church is a 19th-century Roman Catholic church located in Tignish parish, Prince Edward Island, Canada.
 As of 2006, it is the single largest church on Prince Edward Island, measuring 185 feet high.
 It can be clearly seen for 6 miles on flat land, and for many more miles at sea.
 It is perhaps most famous for its widely publicized apparition of Jesus event.
Christianity is and has been the largest religion in Ireland.
 Most Christian churches are organized on an all-Ireland basis, including both the Republic of Ireland and Northern Ireland.
 In the Republic of Ireland, 84.2% of the population adheres to the Catholic Church.
 In Northern Ireland, the various branches of Protestantism collectively form a majority of the population but the single largest church is the Catholic Church which accounts for some 40.8% of the population.
Religion in Scotland includes all forms of religious organisation and practice.
 Christianity is the largest faith in Scotland.
 In the 2011 census, 53.8% of the Scottish population identified as Christian (declining from 65.1% in 2001) when asked: "What religion, religious denomination or body do you belong to?"
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 The Church of Scotland, a Presbyterian denomination often known as The Kirk, is recognised in law as the national church of Scotland.
 It is not an established church and is independent of state control.
 However, it is the largest religious grouping in Scotland, with 32.4% of the population according to the 2011 census.
 The other major Christian church is the Roman Catholic Church, the form of Christianity in Scotland prior to the Reformation, which accounted for 15.9% of the population and is especially important in West Central Scotland and the Highlands.
 Scotland's third largest church is the Scottish Episcopal Church.
Christianity is the largest religion in Northern Ireland.
 According to a 2007 Tearfund survey, Northern Ireland was the most religious part of the UK, with 45% regularly attending church.
North Point Community Church is a non-denominational, evangelical Christian megachurch located in Alpharetta, Georgia, a suburb of Atlanta.
 North Point currently averages more than 36,000 people in attendance among its six campuses each week, making it the largest church in Metro Atlanta and according to "Outreach Magazine", the largest church in the United States as of 2014.
 Andy Stanley is the senior pastor.
 Clay Scroggins serves as the church's lead pastor and, in turn, leads the North Point Community Church staff.

Question: What is the single largest church in the most religious part of the UK?
Answer: Catholic Church