Dr William Francis Norman O'Loughlin was born in Tralee, Co Kerry, Ireland on 22 October 1849; he was the second son of William O’Loughlin and his wife Eliza née Matthews. He had an elder brother, Edmund Matthew (b. 25 November 1847). 

After his parents died when he was young, William was raised by his maternal uncle Benjamin Matthews, a customs official in Co Kerry who had a family of his own. 

Reportedly an alumnus of Trinity College, Dublin, O’Loughlin was registered as a student at Dublin’s Catholic University of Ireland (modern-day University College Dublin) on 8 November 1864. In the winter of 1866 his name appeared on the books of the Medical School of that institution, based at Cecilia Street, Dublin. He graduated in 1869 and remained a devoted former student and forever “looked gratefully to the rock from whence he was hewn.”

Whilst still a young man, ill health persuaded O’Loughlin to pursue his career at sea and he would spend the next forty years of his life there, proving a popular and larger-than-life personality with his fellow crewmen and the passengers. 

A late resident of Liverpool before relocating to Southampton, during the 1890s O’Loughlin served for several years aboard Majestic; prior to being transferred to the Titanic he was surgeon on board the Olympic. According to a colleague Dr J. C. H. Beaumont, O’Loughlin had some misgivings about joining the new ship:

'Whether he had any premonitions about the titanic (I think it is known that (purser) McElroy had) I cannot say, but I do know that during a talk with him in the South Western Hotel he did tell me that he was tired at this time of life to be changing from one ship to another. When he mentioned this to Captain Smith the latter chided him for being lazy and told him to pack up and come with him. So fate decreed that 'Billy' should go on the Titanic and I to the Olympic'
Dr J.C.H. Beaumont in Hyslop et al (1997) Titanic Voices

On 10 April, before Titanic sailed Dr O'Loughlin and his assistant Dr J. Edward Simpson examined the crew muster sheets with Captain Maurice Harvey Clarke, the Board of Trade immigration officer to ensure a healthy crew was aboard. Just one of the many formalities which had to be completed before the maiden voyage could begin

Throughout the voyage he regularly dined with Thomas Andrews and 14 April was no exception. But, according to steward Thomas Whiteley on at least one occasion he dined with Captain Smith and J. Bruce Ismay. Whiteley stated:

Dr. O’Loughlin rose and lifting his glass, exclaimed: ‘let us drink to the mighty Titanic.’ With cries of approval everybody stood up and drank the toast. — North Berks. Herald, April 20, 1912 p.2

After the collision O'Loughlin whispered to stewardess Mary Sloan 'Child, things are very bad'. Reportedly refusing to don a lifejacket, later on in proceedings as the water reached C Deck, O'Loughlin stood quietly with Purser Herbert McElroy, Assistant Purser Reginald Barker and Assistant Surgeon J. Edward Simpson; for a brief time they were joined by Second Officer Herbert Lightoller and the men shook hands and said their goodbyes.

Perhaps the last person to see Dr O'Loughlin was chief baker Charles Joughin; around 1:20 Joughin had retired to his cabin to find some liquor and around 1:45 he noticed Dr O'Loughlin nearby searching for something. Joughin did not ask what he wanted but given the proximity of the pantry, he may have had a similar idea to the baker.

O'Loughlin died in the sinking and his body, if recovered, was never identified.

As an officer of the ship… he made no attempt to escape when the accident happened, but bent all his energies to helping others. It is said that he did not even don a lifebelt. It was a fitting end to an unselfish and self-sacrificing career, one marked at every step by charity, not only that expected of the doctor, but signalled by so liberal giving of money as to leave him usually straitened in his circumstances… — Irish Independent, 7 May 1912

Mourned universally, a Requiem Mass was held for Dr O’Loughlin in the ornate Byzantine-style Catholic University Church, of which he had been a member; the event brought out a large crowd, with many alumni in attendance.

His brother Edmund, a resident of Paris where he lived with his wife, the former Valentine Rosalie Petit, died on 21 October 1919.