Downer was born in South Australia in 1951 and is a member of the Liberal Party of Australia. The Downer family have been involved in politics for over a century. A draft of the Australian constitution was created in the Downer family home prior to federation in 1901. His father was Sir Alexander Russell Downer and grandfather was Sir John William Downer. Downer was educated at Geelong Grammar School. He obtained a Bachelor of Arts with Honours in Politics and Economics from the University of Newcastle upon Tyne, UK, and holds a Doctor of Civil Laws (honoris causa), also from the University of Newcastle upon Tyne.
He was elected to the Adelaide Hills seat of Mayo in 1984. He served in various shadow cabinet position, becoming Leader of the Opposition in 1994. During his time in opposition he made many controversial decisions including addressing the far-right group League of Rights meeting in 1987 thinking it was a Christian rally. His most famous mistake was as Leader of the Opposition when he joked after the launch of the "Things that Matter" policy, that they would call the Liberal Party's policy on domestic violence "Things that Batter". Afterwards poor opinion polling and low party donations accumulated in a meeting of Howard, Peter Costello and Downer in which they agreed for Downer to hand over the party's leadership to Howard without a formal challenge.
After the landslide election in 1996 Downer became foreign minister, a position he held for a record 11 and a half years. One of the key features of his time was the re-strengthening of ties with the United States of America which had been neglected by the Hawke and Keating Governments which had primarily focused on Asia. Downer is credited with being a master of foreign affairs as he was able to ally Australia closely with the US, as well as getting Australia a seat at Association of Southeast Asian Nations - something Australia has not had since the organization was formed in 1967 - to the surprise of most critics who said that focusing on the US would come at the expense of regional relations. Downer was a strong support of both the Afghanistan and Iraq wars.
On July the 3rd 2008, following the defeat at the November 2007 election, Downer announced his retirement from politics and said he would give his resignation as the Member for Mayo to the Governor-General on the 14th of July. Following his retirement he was made Visiting Professor of International Politics at the University of Adelaide's School of History & Politics by the Vice Chancellor Professor James McWha. The position entitles him to call himself Professor Downer.