Mary Jane Kelly was born in Limerick in 1863 and her large family moved to Wales when she was young. Her father John worked in an iron works, and Mary had seven brothers and at least one sister She was a tall (5’7”), pretty girl with blue eyes and though she may have been illiterate was reported to be very clever and to have some artistic ability.

When she was about 16 she married a coal miner named Davies, who was killed about 1881 in a mine explosion. Mary stayed for eight months in an infirmary in Cardiff, before moving in with a cousin and starting to work as a prostitute.

Mary moved to London in 1884 and found work in a West End brothel. Reportedly, she was invited by a client to France, but returned to England within two weeks, having disliked her life there. Gravitating toward the poorer East End of London, she lived for a time near the Commercial Gas Works in Stepney. When drunk, Kelly would be heard singing Irish songs. A friend commented that "she was a very quiet woman when sober but noisy when in drink."

In 1888 Mary moved in with Barnett, they lived in a single room at 26 Dorset Street, Spitalfields. Barnett worked as a fish porter at Billingsgate Fish Market, but when he fell out of regular employment and tried to earn money as a market porter, Kelly turned to prostitution again to pay their rent.

She was only 25 when she was found brutally murdered in Whitechapel on 9 November 1888. Mary Jane was a Catholic, and she is buried in St Patrick’s cemetery in Leytonstone.