Henry Daniel Sinclair (1818–1868) was an explorer and founder of Bowen, Queensland, Australia. Captain Sinclair discovered Port Denison (the port of Bowen) in 1859 in the cutter Santa Barbara.
During the second half of the nineteenth century the expansion of settlement in North Queensland caused increasing problems with the carriage of freight to and from southern supply centres. In response to this problem the New South Wales Government, in 1859 (i.e. prior to the separation of Queensland), offered a reward for the discovery of a suitable harbour north of Port Curtis (Gladstone) that could be more easily accessed by northern settlers. Captain Henry Daniel Sinclair, owner of the 9-ton ketch Santa Barbara, departed Sydney in August 1859 in order to locate such a suitable harbour, undertook this mission. On the 15th October 1859 Sinclair's party found such a site, and subsequently named it Port Denison. However, by the time Sinclair returned to claim his reward, the separation of Queensland had occurred and neither the New South Wales nor Queensland Government each believed the other was responsible for paying the reward and so Sinclair was never paid.
The first settlers began arriving as early as 19 March 1861. The settlement was officially proclaimed on the 11th April 1861 (after the separation of Queensland), and named Bowen after the Queensland Governor, Sir George Ferguson Bowen. The township of Bowen quickly grew to support the northern pastoral industry as a strategically placed supply centre and over the course of several decades the town developed into a thriving commercial port.
Sinclair served as harbourmaster in Bowen for a number of years.
In 1868, Sinclair purchased the schooner Telegraph to take up beche-de-mer fishing between Port Denison and Cape York. However, before the vessel was ready to take to sea, Sinclair died aged 50 in a sailing accident in Cleveland Bay (off Townsville) while participating in the St Patrick’s Day Regatta. He was buried in the West End Cemetery in Townsville on St Patrick's Day with the burial service read by an old friend and shipmate, James Gordon. Sinclair was one of the early burials in the cemetery and his sandstone headstone is believed to be the oldest surviving headstone in the cemetery. He left a widow and five children.