Hans Sauer (11 June 1857 - 28 August 1939) was a South African born medical doctor, lawyer, adventurer and businessman. He is regarded as a Rand Pioneer, arriving in Johannesburg in 1886 shortly after the discovery of gold and was the town's first district surgeon. He is linked with the creation of Rhodesia.
Johannes Sauer was born in Smithfield, Orange Free State in 1857. He is the brother of J.W. Sauer. His father was the town and district Landdrost. His father, Johannes J. Sauer, moved the family to Aliwal North were he practised law and farming but died in 1870. His mother was Elizabeth W.S.M. Kotz. Sauer was schooled at Burgersdorp, Cape Colony from 1872 until 1876. After completing school, he was sent to the London to continue his studies at University College London. By October of the same year, he went to Edinburgh to study medicine and graduated in 1881 with a MB and CB.
He returned to South Africa in 1882 and headed to Kimberley diamond fields and offered the job as a Quarantine Officer on the Modder River, examining people heading to the town. A year later he left his position and joined Dr. Oskar Sommershield in a hunting trip that took him through the Transvaal and into Mozambique to Lourenco Marques. Leaving that town, they headed back into the Eastern Transvaal to the goldfields of Barberton. At Lydenburg, he met Leander Starr Jameson. He would then return to Kimberley after the outbreak of a smallpox epidemic and remained until 1886.
In 1886, he was employed by Cecil John Rhodes and Charles Rudd with a 15% share, and he headed to Johannesburg to join the Witwatersrand Gold Rush where Sauer bought up mining claims along the Main Reef on behalf of the men. In a growing mining town, he soon had many interests but his main appointment was on 6 March 1887 as Johannesburg's first district surgeon with friend Ignatius Ferreira sometimes acting as his anaesthetist. Other positions held included chairman of the Diggers Committee, chairman of the Rand Club and a chief consulting surgeon at the new Johannesburg Hospital as well as investing in coal mining in the East Rand to supply fuel to the gold mines. He was involved with the first hospital in the town, an extension of the jail hospital on 1 August 1888 and involved in the new Johannesburg Hospital, a dedicated building that opened on 29 March 1889. He would marry Cecile J. Fitzpatrick in 1890, the sister of Sir Percy Fitzpatrick.