Converts to Roman Catholicism from atheism or agnosticism

Reinhard Johannes Sorge (29 January 1892 – 20 July 1916) was a German dramatist and poet. He is best known for writing the Expressionist play The Beggar (Der Bettler), which won the Kleist Prize in 1912 and almost singlehandedly created surrealist theatre and modern theatrical stagecraft. After being subsequently received into the Roman Catholic Church, Sorge began an effort to bring the Catholic literary revival into the literature of the Germanosphere. Instead, Sorge was conscripted into the Imperial German Army in World War I in 1915. He was killed in action during the Battle of the Somme in the summer of 1916. Sorge's Der Bettler, however, received a posthumous premiere in a groundbreaking production by legendary Austrian Jewish stage director Max Reinhardt in 1917.

Clemente Rebora (6 January 1885 – 1 November 1957) was a poet from Milan, Italy. He received a degree in Italian literature in Milan. In the early 1900s he worked for the magazines La Voce, Rivista d’Italia and La Riviera Ligure.His book Frammenti Lirici (Italian: Lyrical Fragments) was published in 1913. From 1913 to 1922, he wrote anonymous "Songs" and lyrics. After World War I Rebora began to work as a teacher.Previously an atheist, he had a spiritual crisis in 1928 and became a devout Catholic. In 1930, he entered a seminary; in 1936, he became a Rosminian priest. After this, his work became religious in orientation, but his work is popular beyond Catholic circles for its treatment of metaphysics and physics. He is somewhat controversial for his friendship with Julius Evola, but the friendship seems to have been largely based on his hope Julius would convert to Christianity. When this hope grew dim the friendship declined.

Ferdinand Vincent-de-Paul Marie Brunetière (19 July 1849 – 9 December 1906) was a French writer and critic.

André Frossard (14 January 1915 – 2 February 1995) was a French journalist and essayist.

Gerard Kornelis van het Reve (14 December 1923 – 8 April 2006) was a Dutch writer. He started writing as Simon Gerard van het Reve and adopted the shorter Gerard Reve [ˈɣeːrɑrt ˈreːvə] in 1973. Together with Willem Frederik Hermans and Harry Mulisch, he is considered one of the "Great Three" (De Grote Drie) of Dutch post-war literature. His 1981 novel De vierde man (The Fourth Man) was the basis for Paul Verhoeven's 1983 film.
Reve was one of the first homosexual authors to come out in the Netherlands. He often wrote explicitly about erotic attraction, sexual relations and intercourse between men, which many readers considered shocking. However, he did this in an ironic, humorous and recognizable way, which contributed to making homosexuality acceptable for many of his readers. Another main theme, often in combination with eroticism, was religion. Reve himself declared that the primary message in all of his work was salvation from the material world we live in.
Gerard Reve was born in Amsterdam, Netherlands, and was the brother of the Slavicist and essayist Karel van het Reve, who became a staunch anti-communist in his own way; the personal rapport between the brothers was not good. They broke off relations altogether in the 1980s.

Charles Pierre Péguy (French: [ʃaʁl peɡi]; 7 January 1873 – 5 September 1914) was a French poet, essayist, and editor. His two main philosophies were socialism and nationalism; by 1908 at the latest, after years of uneasy agnosticism, he had become a believing (but generally non-practicing) Roman Catholic.
From that time, Catholicism strongly influenced his works.