Matthew Hamilton Gault was born on July 18, 1822, in Strabane, Tyrone County, Northern Ireland, the brother of Andrew Frederick Gault (1833–1903), the Cotton King of Canada.

He was an Irish-Canadian financier and politician. In 1841, his family emigrated to Lower Canada, settling in Montreal, Quebec. His father Leslie Gault (1787-1843), a merchant and shipowner, died soon after and left the family with huge financial losses. In 1851, he was appointed agent to the Mutual Life Assurance Company of New York and the Western Assurance Company of Toronto, Ontario. By the early 1860s, he was the secretary-treasurer of the Montreal Permanent Building Society, which became the Montreal Loan and Mortgage Company in 1875. He was named its president in 1877, a position he held until his death. He was also the manager of the Royal Canadian Bank of Toronto in Montreal (1866-1870) and from 1879 he was a director of the Royal Insurance Company of England. He became President of the Exchange Bank of Canada, director of the Richelieu and Ontario Navigation Company, director of the Windsor Hotel, trustee and treasurer of the Mount Royal Cemetery, a director of the Montreal General Hospital, and of the Montreal Sailors Institute. For many years he was a justice of the peace of the city of Montreal and a warden of Christ Church Cathedral. He was a founder and the first president of the Irish Protestant Benevolent Society of Montreal.

In 1854, he married Elizabeth Joanna Bourne (1834–1908). They were the parents of sixteen children, eleven of whom lived to adulthood. He died on June 1, 1887, in Montreal, Quebec.