John Sydney Swan (12 January 1874 – 18 April 1936) (sometimes seen as Sidney) was a New Zealand architect, the designer of houses and churches in Wellington, New Zealand. He was articled to Frederick de Jersey Clere and was at one time a partner with Clere. Buildings he designed include Erskine College and St Gerard's Church and Monastery, and various commercial buildings, houses and Wellington Harbour Board buildings.
He was born and died in Wellington, and built the house, The Moorings in Glenbervie Terrace, Thorndon in 1905. His younger brother Francis Herbert Swan (1885–1956) also lived in Glenbervie Terrace, and in 1915 they formed an architectural partnership; Swan and Swan; later Swan, Lawrence and Swan.
He was a yachtsman, and Commodore of the Royal Port Nicholson Yacht Club.
He married Gertrude Mary Holcroft in 1899, they had three sons and one daughter.