Miss Mary Josephine Gregson was born in Liverpool, Lancashire, England on 31 March 1867 and baptised the same day in St Nicholas' Church.

Hailing from a Roman Catholic family, she was the eldest child of Henry Gregson (b. 1845), a seaman, and Ellen Whitehead (b. 1842). Details about her father are unclear and her mother's exact origins are also lacking; she apparently hailed from Great Crosby but also claimed to be Irish by birth.

She had two known siblings: Henry Joseph (b. 1869) and Ellen (b. 1871).

Mary appears on the 1871 census living with her family at 99 Berry Street, Bootle; her mariner father is absent. In February 1873 her father died at sea aged 27 and her mother remarried the following year to John Joseph McAdam (1845-1904), a bookkeeper.

From this union Mary gained nine half-siblings: John Francis (b. 1875), Edward Francis (b. 1877), Lawrence Francis (b. 1879), Theodore (b. 1880), Winifred Mary (b. 1881), Catherine Josephine (b. 1884), Gertrude (b. 1885), Francis (b. 1887) and Joseph Placid (b. 1890).

The large family appeared on the 1891 census at 10 Newlands Street, Everton and Mary was described as a shop girl. By 1901 her home address was 5 The Green, Great Crosby but Mary was not listed there with her family and was presumably at sea. She first appears on records serving aboard Teutonic in 1895 and was shown as a stewardess on several voyages in 1904 aboard Cedric, prior to which she had served aboard Romanic. On one voyage aboard Cedric in September 1904, three of her shipboard colleagues were several other Titanic luminaries: Abraham Mishellany, Elizabeth Leather and Andrew Latimer. Her sister Ellen also worked at sea for a period.

When she signed-on to the Titanic on 6 April 1912, Mary gave her local address as 28 Lawland Road, Southampton; her Liverpool address was 2 Preseland Road where her family lived. Her previous ship had been the Olympic and as a stewardess she received monthly wages of £3, 10s.

Miss Gregson survived the sinking together with fellow stewardess Mrs Kezia Roberts, but the exact boat is not known for certain. She was not called to testify at either the British or American Inquiries into the sinking.

Mary never married and continued working at sea, going on to serve aboard Cedric, Celtic and Baltic, among other ships. Tragedy again struck the family when her younger brother Henry drowned on 30 June 1913 whilst swimming in Salthill, Co Galway, Ireland.

Mary spent her last days living at 3 Weld Road, Birkdale, Lancashire. On 20 February 1923 she arrived in New York City aboard the Adriatic. Three days later at St Vincent's Hospital she died due to cerebral embolism and heart failure.

Her body was returned to England and she was buried with her family at the cemetery of St. Peter and Paul Church, Crosby, Liverpool. Her estate worth £160, 5s was left to her mother Ellen who would die in November the following year.