Robert Henry Mariner Forster 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. In 1862 he was elected to the New South Wales Legislative Assembly for New England, but he was defeated in 1864. He returned in 1870 as the member for Goldfields North.
He was defeated in 1872, re-elected in 1875 and defeated again in 1877.