William John Butt was born in Southampton, Hampshire, England on 18 May 1881. He was the son of William Butt (1848-1932) and Emily Woodcock (1852-1929), both Southampton-natives who had married in 1873.

William was one of ten children born to his parents, his siblings being: Emily Leah (b. 1875), Sabina Mary (b. 1876), Elizabeth Maud (b. 1877), Elizabeth Augusta (b. 1879), Cecelia Jane (b. 1884), Edith Fanny (b. 1886), Albert Edward (b. 1889) Robert Henry (b. 1890) and George Leonard (b. 1894).

William first appears on the 1891 census. At the time he and his family were living at 26 Kent Road, Freemantle, Southampton and his father was described as a musician. The family are listed at 4 Gordon Terrace, Heysham Road on the 1901 census but William is absent, perhaps already at sea. By the time of the 1911 census William and his family are living at 36 Richmond Road, Freemantle, Southampton and he is described as an unmarried Royal Naval fireman.

When he signed-on to the Titanic, on 6 April 1912, Robert gave his address as 6 Cawte Road, (Southampton). His last ship had been the Olympic. As a fireman he received monthly wages of £6. Also serving aboard, as a first class steward, was his brother Robert Henry Butt.

William Butt, along with his brother, died in the sinking and both their bodies were recovered. His body, recovered by the Mackay-Bennett as #77, was buried at sea.

The following death notice appeared in the Southampton Times (unknown date):

BUTT--April 15th, on s.s. Titanic, William, aged 30, and Robert aged 21, the dearly loved sons of William and Emily Butt, of 6. Cawte Road, , Freemantle, Southampton. Deeply mourned by all the family. "Peace, Perfect Peace."