Background
He was born at Holymount in County Mayo to farmer Henry O'Brien and Catherine Browne.
He was born at Holymount in County Mayo to farmer Henry O'Brien and Catherine Browne.
He worked on his uncle's properties before migrating to Sydney via Calcutta. From 1821 he farmed at Bathurst, and he also acquired a sheep station at Yass Plains. In 1860 he was elected to the New South Wales Legislative Assembly for Yass Plains, but he resigned in 1861.
O'Brien died at Douro near Yass Plains in 1866.