Camillus de Lellis was born at Bucchianico (now in Abruzzo, then part of the Kingdom of Naples). His mother died while he was still a child and his father was an officer in both the Neapolitan and French royal armies. As a consequence Camillus grew up neglected. Camillus joined the Venetian army while still only a youth. After his regiment was disbanded in 1574 Camillus worked in a hospital for incurables, however his aggressive nature and excessive gambling led to his dismissal. He later rejoined the Venetian army and fought in a war against the Turks. After the war he returned to the hospital in Rome from which he had been dismissed, he became a nurse and later director of the hospital.
Camillus established the Order of Clerks Regular Ministers to the Sick, better known as Camillians. His experience in wars led him to establish a group of health care workers who would assist soldiers on the battlefield. The red cross on their cassock remains a symbol of the order today. Members also devoted themselves to the plague-stricken. Camillus was so distressed at how hopeless plague cases were treated during his time that he formed the "Brothers of the Happy Death," for plague victims. It was for the efforts of the Brothers and his alleged supernatural healings that the people of Rome credited Camillus with ridding the city of a certain plague and, for a time, Camillus became known as the "Patron Saint of Rome".
In 1594 Camillus also led his friars to Milan where they attended to the sick of the Ca' Granda, the main hospital of the city. A memorial tablet in the main courtyard of the Ca' Granda commemorates his presence there.
Throughout his life Camillus' ailments caused him suffering, but he allowed no one to wait on him and would crawl to visit the sick when unable to stand and walk. It is said that Camillus possessed the gifts of healing and prophecy. He died in Rome in 1614.
Camillus was beatified by Pope Benedict XIV in the year 1742, and canonized by him four years later in 1746.