Dean Harold Jaensch AO (born 1936) is an Australian political scientist and a retired Professor of Political and International Studies at The Flinders University of South Australia. Jaensch was awarded a Bachelor of Arts (Honours), a Master of Arts and PhD from the University of Adelaide. He wrote many highly regarded books (14) on political parties, electoral politics and voting behaviour in Australian politics, and also focussed on South Australian and Northern Territory politics, federalism within the Anglosphere and empirical methodology.
He lectured at Flinders University from the early 1970s until retirement in 2001, he remains an adjunct Professor with the Department of Politics and Public Policy. For decades he was prominent political commentator/psephologist for the Australian Broadcasting Corporation and a frequent contributor to local radio in South Australia. Currently, Jaensch is a columnist for The Advertiser newspaper and an occasional lecturer at Flinders University. He continues to speak on public affairs and the machinations of State and national government. Jaensch advocates proportional representation and an end to compulsory voting in Australia (though not necessarily compulsory enrolment).
- A Plague On Both Your Houses: Minor Parties in Australia, Allen & Unwin, Sydney, 1998 (with David Mathieson).
- Power Politics: Australia's Party System, 3rd ed., Allen & Unwin, Sydney, 1994.
- The Liberals, Allen & Unwin, Sydney, 1994.
- The Politics of Australia, Macmillan, Melbourne, 1992.