Sir James Willson Agnew KCMG (2 October 1815 – 8 November 1901) was an Irish-born Australian politician, who was Premier of Tasmania from 1886 to 1887.

Agnew was born in Ballyclare, Ireland and educated at London, Paris and Glasgow; he qualified for the medical profession, M.R.C.S.

He decided to settle in the west of Port Phillip District (now the Western district of Victoria), but not enjoying the life, went to Melbourne, where he was offered the position of private secretary to John Franklin, then governor of Van Diemen's Land (now Tasmania).

After his return he was elected to the Tasmanian Legislative Council in 1884, and on 8 March 1886 he took over from Adye Douglas and formed a ministry in which he was premier and chief secretary.

Agnew was the founding President of The Art Society of Tasmania, serving for seventeen years.