Walter Duffield (1816 – 5 November 1882) was a pastoralist and politician in colonial South Australia, Treasurer of South Australia 1865 to 1867.
Duffield was born in Great Baddow, Essex, England, son of William Duffield, a farmer. Walter arrived in South Australia in the William Barras in December 1839. His first occupation was as manager for fellow-passenger Jacob Hagen's estate at Echunga, where his wine was some of the first produced in the colony. He left Echunga to build up the Para Para estate and produced hams, wines and orchard fruit; he later had 40,000 Merino sheep.
He started business in Gawler as a flour miller ("The Victoria Mill") and merchant in September 1847, and, in conjunction with Harrold Brothers as Duffield, Harrold and Company (later Duffield, Harrold and Hurd), owned Weinteriga and Outalpa stations.
Duffield was member for Barossa in the South Australian House of Assembly from 9 March 1857 to 6 April 1868 and from 14 April 1870 to 13 December 1871, and was Treasurer in the John Hart Government from 23 October 1865 to March 1866, and in the Ministry of James Boucaut, which succeeded it, from the latter date till 3 May 1867. Duffield subsequently sat in the South Australian Legislative Council from 3 April 1873 to 27 May 1879, when every four years one third of the Legislative Council was elected by the whole colony as one electorate "The Province".
Duffield died in Gawler, South Australia on 5 November 1882 and was buried in Willaston cemetery. Duffield was survived by his wife Phoebe, née Johnstone (married 7 March 1842) and by one son and five daughters.