The 19th century AD consists of the years 1801-1900.
- Discovery of several New Testament apocrypha documents opens a scholarly debate on Early Christianity, a debate that continues today.
- Charles Darwin and other biologists propose the theory of Evolution. Geologists date the Earth to over five billion years of age. Fundamentalist Christianity begins as a movement that believes these scientific findings are contrary to scripture.
- Friedrich Nietzsche declares that God is dead. In 1900, God will declare that Nietzsche is dead.
- Karl Marx publishes The Communist Manifesto, which dismisses religion as a drug used by the oppressive ruling class to placate the oppressed working class.
- Birth of Neocalvinism.
- 1829 - Pope Pius VII succeeds Pope Leo XII as the 253rd pope.
- 1829 - Religious freedom is restored in Ireland.
- Restorationism seeks to restore what they believe is the original form of antenicene or Early Christianity.
- 1830 - Joseph Smith, Jr. publishes the Book of Mormon and founds the Church of Christ, the first Mormon church. The church is renamed the Church of Jesus Christ of Latter-day Saints in 1838.
- 1830 - Sidney Ridgon baptized.
- 1830 - Geologist and clergyman Sir Charles Lyell released the first of a three volume creationist publication titled Principles of Geology.
- 1870 - Unification of Italy, which reduces the Papal States to the Vatican City. First Vatican Council upholds the doctrine of papal infallibility, but is rejected by the Old Catholic Church.
- 1871 - The Anglican Church of Ireland disestablished by the Irish Church Disestablishment Act.
- 1870s - Charles Taze Russel starts a Bible study group that becomes the Jehovah's Witnesses.
- 1878 - East London Christian Mission renamed The Salvation Army by General William Booth.
- 1878 - Niagara Bible Conference establishes Fundamentalist Christianity as a distinct movement.
- 1880 - The Salvation Army begins work in Australia, Ireland (Ulster) and the United States.
- 1895 - The Salvation Army begins work in Japan.
- Bramwell Booth, 1856; Second General of The Salvation Army, 1912 - 1929.
- Catherine Booth, 1829; the Mother of The Salvation Army, 1878 - 1890.
- William Booth, 1829; Founder and First General of The Salvation Army, 1878 - 1912.