William McMinn (1844 - 14 February 1884) was an Australian surveyor and architect, based in Adelaide. He was born in Newry, County Down, Ireland, and came to Adelaide at the age of six.
After completing school, he was apprenticed to the architect James MacGeorge, but first practiced as a surveyor. He was involved in Boyle Travers Finniss's ill-fated 1865 expedition to Northern Australia surveying the area around the Adelaide River. Following the desertion of a majority of the party to Singapore, McMinn and 5 others purchased a 23-foot open boat which they named the Forlorn Hope and sailed it 2000 miles to Champion Bay, Geraldton, Western Australia. He was later involved in the 1872 surveying of the Overland Telegraph from Port Augusta to Darwin.
McMinn began practising as an architect in 1867, sometimes in partnership but usually independently. He designed many grand private residences, but also designed or assisted in the design of many of Adelaide's grand public buildings. Whilst in partnership with Edward John Woods, he designed the original Venetian Gothic building of the University of Adelaide, condidered his greatest work.
McMinn married Mary Francis Muirhead at Glenelg in 1877, with whom he had two daughters. He died in North Adelaide, aged forty, on 14 February 1884.