Daniel O'Sullivan was born in Kilmurry, in the diocese of Cork, on 18 January 1858. He died at Marseille, France, on 13 July 1930.

Daniel was a school-master in Cork city when in 1880, wishing to become a missionary priest, he approached Francois Devoucoux, first S.M.A. superior in Ireland. With great energy Daniel undertook the study of Latin at the Society's apostolic school on the Blackrock Road, Cork, so as to be able to present himself at the major seminary, on Cours Gambetta, Lyon (France) in the autumn of 1881. He took his oath of Society membership at Christmas, 1882, and was ordained a priest, in the seminary chapel at Lyon, on 25 July 1885. Two other Irishmen were ordained on the same occasion, Andrew Dornan and Michael John Healy. When the Irish Province of the Society was formed in 1912 Daniel remained attached to the Generalate and was incorporated into the Lyon Province when it was founded in 1927.

At that time the Society, as well as the Egyptian mission, was in the throes of a serious financial crisis. Daniel was called upon to take up the role of find-raiser and promoter for the Society, a task he was to discharge with great distinction for almost 30 years. He collected throughout the world, visiting several times Australia, New Zealand, Tasmania, the U.S.A., England, Ireland, and Argentina- He is known to have traversed the Mediterranean 27 times and the Atlantic 38 times. He crossed the Indian Ocean 11 times.

Daniel acquired the name of being a 'conferencier de grand reputation', holding his audiences spellbound with his descriptions of missionary life and galvanising their support for the work. His talents as a writer were no less considerable; his output was prolific, to be found in numerous revues, magazines and journals of the period; he also had published several pamphlets and brochures inspired by his journeys and by the history of the Society's missions. Among the titles published under his name were the following: What we have accomplished on the Guinea Coast. on the Niger River. and by the Banks of the Ni1e, The S.M.A. - its heroic work of Charity in Africa; Homeward through Egypt; and The Land of the Pyramids and the White Man's Grave.

In 1927 Fr. O'Suilivan fell into poor health and in hope of a recovery he took up residence in tht S.M.A. sanatorium at La Croix, Var, France. There, from his sick bed, he continued to type out promotional material and, above all, letters to benefactors. However, his health deteriorated and he was hospitalised in Marseille. He spent his last days with the sisters at St. Joseph's nursing home, in Marseille. Preserved in the archives of the Irish Province at Blackrock Road there is an account of Daniel's last days written by the Superior General, Jean-Marie Chabert, to Denis' brother.

'Fr. O'Sullivan who, as you know, was being taken care of in our sanatorium, had of late expressed his desire to have a change, complaining that the climate of La Croix was too hot for him. He was then brought to Marseille and placed in a clinical hospital to receive there a special treatment. But his health, instead of improving, soon became very bad. He was then carried to St. Joseph's and entrusted to the care of the good sisters in charge of the hospital. One of our priests in residence at Marseille used to visit him often. It was soon obvious that, owing to the bad condition of the heart and of the liver, the good Father's life would not last long. He was then fortified with the last sacraments of the Church, submitted to the will of God, took up the cross of his agony and breathed his last. He was buried in the presence of the vicar general of the S.M.A., Edouard Lacqueyrie, the superior of our seminary at Lyons, Joseph Delhommel, and the priests of the procure.

He is buried in Marseile, France.