Robert Henry Mariner Forster (1818 – 2 February 1880) was an Australian politician.
He was born at sea near Corfu to Henry and Margaret Forster; his father would later serve as governor of Goulburn Gaol.
He arrived in Australia around 1836 and became a solicitor, based ar Armidale.
On 9 September 1847 he married Maria Ann Morris, with whom he had seven children.
In 1862 he was elected to the New South Wales Legislative Assembly for New England, but he was defeated in 1864.