Siméon-François Berneux was born in France May 14, 1814. He entered the Seminary of Foreign Missions in 1831 when he was seventeen. In 1843 he entered the Seminary of Le Mans to complete his studies. He was ordained on May 20, 1837, and appointed as Professor of Theology at the Foreign Missions Seminary in October 1838.
Berneux left Le Havre on February 12, 1840, and arrived at Anyer in Java on May 31. He spent the summer in Manila before sailing to Macau. In January 1841 he sailed to Tonkin. In Vietnam he was imprisoned and taken to Huế for trial. He arrived on May 28. In 1842 he was convicted of preaching Christianity and sentenced to death. That death sentence was indefinitely postponed. He was released on March 12, 1843, and set sail to return to France. When he arrived at the Isle of Bourbon, he received permission to return to Macao. He was appointed to begin missions in Manchuria, and arrived in the Liaodong Peninsula on March 15, 1844.Berneux was consecrated as bishop on December 27, 1854. He was appointed Bishop of Capsus and Apostolic Vicar of Korea. The previous Apostolic Vicar of Korea, Jean-Joseph-Jean-Baptiste Ferréol, had been consecrated in 1843 and ministered in Korea from 1845 until his death in 1853. Berneux sailed from Shanghai to Korea in January 1856 on a Chinese ship. He arrived in Korea on March 15. They met a vessel owned by Korean Christians on Good Friday and were landed near Seoul. Entering the city on foot, Berneux and his company were taken to the house of Marie-Nicolas-Antoine Daveluy, a French priest who had come to Korea along with Bishop Ferréol. Berneux set up a residence in Seoul, living and working secretly.
In 1866 Berneux was arrested and put on trial. In February 1866 he was repeatedly tortured and interrogated, and sentenced to death. He was executed by decapitation on March 8, 1866. Daveluy served as Apostolic Vicar for a short time until he was also executed on March 30. The deaths of Berneux and other Catholic missionaries in Korea was followed by a French punitive expedition that reinforced the Korean policy of isolationism.