The coastal townsite of Port Denison is located in the northern agricultural region, 365 kilometres north northwest of Perth and three kilometres from Dongara. The area was referred to as Irwin Port (being near the mouth of the Irwin River) in 1866, but when officially named and gazetted the following year later it became Denison. It is believed named after Sir William Denison, Governor of Tasmania, who visited Western Australia in 1851 in connection with the transportation of convicts to the state. The name was changed to Port Denison in 1973 at the request of the Shire of Irwin, as this was the name by which the town was locally known.