Desmond Joseph O'Malley was born on 2 February 1939 in Limerick City. He was educated in Limerick and University College Dublin and qualified as a solicitor in 1962. In 1968 he was elected to the Dáil as a Fianna Fáil TD following the death of his uncle, Donagh O'Malley. In 1969 he became Parliamentary Secretary to the then Taoiseach, Jack Lynch.
Between 1970 and 1973 he was appointed to the Cabinet as Minister for Justice. During this time O'Malley introduced new legislation and took strong action against the IRA. In 1977 O'Malley was appointed Minister for Industry and Commerce in the newly formed Fianna Fáil government. Two years later in 1979 he supported George Colley in his bid to become leader of Fianna Fáil, however Charles Haughey was the successful winner. Throughout 1982 Haughey was challenged three times for the leadership of the Party. On these occasions O'Malley was seen as his likely successor. However, on all occasions Haughey won by a narrow majority of votes caused by open ballots. Haughey still appointed O'Malley as Minister for Industry, Commerce and Tourism when Fianna Fáil returned to power. In the short-lived 1982 government O'Malley became Minister for Trade, Commerce and Tourism. He resigned in October of that year after refusing to support Haughey in a leadership challenge.
In 1985 he was expelled from Fianna Fáil for failing to support the party in a controversial vote about contraception. Later that year he formed his own party - the Progressive Democrats (PD). In 1989 the Progressive Democrats and Fianna Fáil formed a coalition government - the first in the history of Fianna Fáil. O'Malley became Minister for Industry and Commerce. In 1992 Albert Reynolds became Taoiseach. Reynolds accused O'Malley of being 'dishonest' when giving evidence at a tribunal. The Progressive Democrats immediately withdrew from the government and a general election was called.
In October 1993 O'Malley retired as leader of the Progressive Democrats. He was succeeded by Mary Harney. In 1994 O'Malley ran for the European Parliament but was defeated by Pat Cox. In the 2002 general election O'Malley's daughter, Fiona, was elected to the Dáil as a PD candidate.