Mr William Henry Marsh Parr was born in Hindley Green, Lancashire, England on 10 October 1882.

He was the son of John Turner Parr (1854-1913) and Hannah Marsh (1849-1922), both Lancashire natives. His father, an office caretaker, was married to Hannah Marsh in Manchester in 1881 and William became one of five children, three of whom survived infancy. His surviving siblings were: Hannah (b. 1884) and Fanny Ann (b. 1888).

When the family appeared on the 1891 census they were living at an address in Chorley New Road, Horwich, Lancashire and they would still be at this address by the time of the 1901 census. At the time of the latter record William was described as an apprentice electrical engineer. 

He served his apprenticeship with the Electrical Department of the Lancashire and Yorkshire Railway and in whose service he remained until early 1910. He was then appointed to Harland & Wolff in March that year as an assistant manager in the electricians' department, overseeing the fitting-out of ships. He supervised the installation of the electric plant aboard both Olympic and Titanic. 

Parr was married in Cheshire in the latter half of 1910 to Gertrude Poole (b. 1881 in Nantwich, Cheshire), daughter of Joseph and Elizabeth Poole. He and his new bride returned to Belfast where they made their home; the couple appear on the 1911 census living at 16 Elaine Street, Cromac, south Belfast and he was described as a managing electrical engineer. They would later have one child, a daughter named Dorothea Kathleen who was born on 5 January 1912. Despite only two years in Belfast, Parr had made many friends and acquaintances in that city and he was also a teacher in the University Road Methodist Church Sunday School where he was a respected member.

Parr was one of the nine-strong "guarantee group" of Harland and Wolff employees chosen to oversee the smooth running of the Titanic's maiden voyage. 

During the evacuation first-class passenger Anna Warren spotted Parr somewhere on D-deck near the forward first class staircase; she approached him and asked for an explanation as to what was happening; he did not answer and brushed past on his way to the stairwell.  

William Parr, like the rest of his counterparts, died in the sinking. His body, if recovered, was never identified.

According to the Staffordshire Sentinel (20 April 1912) his wife of eighteen months had gone to stay with her family in Northwich, Cheshire for the duration of her husband's journey; if she ever returned to Belfast is not certain.

Gertrude was never remarried and later resettled in her native Cheshire, living at Wood End Cottage in Chester Road, Sandiway. She died on 8 June 1952.

His daughter Dorothea was married in 1939, becoming Mrs John M. Marks; later a businesswoman, she died near Worthing, Sussex in July 2002. 

William Parr is remembered on his wife's and her parents' headstone in Saint John the Baptist church of England, Hartford, Cheshire West, Cheshire, England.