John Brown Watt, MLC (16 May 1826 – 28 September 1897) was a Scottish-born Australian politician and businessman.
Watt was a member of the New South Wales Legislative Council between 1861 and 1866, before leaving to become a board member of the Imperial Federation League in the United Kingdom.
He was re-elected to the Legislative Council in 1874 and served thereafter until 1890.Outside of politics, he was very much invested in public health.
Among other public health ventures, he was a founder of the Hospital for Sick Children, Glebe (now the Royal Alexandria Hospital for Children); director of the Sydney Infirmary and Dispensary between 1869 and 1873; and director of Royal Prince Alfred Hospital.