William Finlayson (1813 – 18 December 1897) was a churchman and farmer in the early days of South Australia, and father of nine children including two sons prominent in the early days of that colony.
Born in Glasgow, he and his wife, née Helen Harvey (born Edinburgh 1811 – 20 October 1884), arrived at Holdfast Bay on the John Renwick around 7 February 1837, just seven weeks after Governor Hindmarsh. as missionaries with the Baptist Missionary Society of England.
Somehow his missionary ambitions failed to materialise. He found employment with the South Australian Company, keeping sheep at Brownhill Creek with Samuel Sleep. He leased a nearby property of 164 acres from the South Australian Company, which he farmed while living in a cottage in Adelaide. By 1853 he had built a substantial residence "Helenholm" (frequently "Helenholme"), named for his wife, and in 1855 converted his land title to freehold.
He was a member of Robert Cock's 1937 exploration party that climbed Mount Barker and reached Lake Alexandrina. They were fearful of encountering the warlike Peramangk and Kaurna inhabitants, but never saw one, though no doubt their progress was being closely observed.
Adelaide's first Strict Baptist church meeting was held in July or September 1838 at his cottage in Rundle Street (later the site of Charles Birks' shop) with David McLaren acting as pastor.
He was one of the founding members of the first Congregational Church under the leadership of T. Q. Stow, then from 27 September 1857 acted as pastor (initially co-pastor) of Zion Chapel in Hanson Street (later renamed as part of Pulteney Street), a position he held for 40 years. Jacob Abbott was co-pastor for some years before moving to the new church at Stepney 1860 to 1877.