Aden Derek Ridgeway (born 18 September, 1962) is an Australian Democrat politician. During his term he has been the only Aboriginal member of the Australian senate.

He was born in Macksville, New South Wales, as one of the Gumbaynggir people. After leaving school in Year 11, he worked as a boilermaker. He then became involved in the public service. In this role, he engaged in a number of careers, including being a park ranger and working in several New South Wales government departments.

In 1990, he was elected onto the first ATSIC Sydney Regional Council, a position in which he served two terms of office. He joined the Australian Democrats in 1991. In 1995, he became the executive director of the New South Wales Aboriginal Land Council . He continued in this position until 2000.

During 1997-98 he served as the state policy convener for the New South Wales Branch of the Democrats. He was subsequently selected in the first position on the Democrats' Senate ticket at the 1998 election. This led to him becoming only the second Aboriginal member of an Australian parliament, after Neville Bonner.

Ridgeway has served on a number of parliamentary and senate committees. In March, 2001, he addressed the United Nations Special Session on Racism. He also attended the World Conference Against Racism in South Africa in the same year.

In April 2001, he was appointed deputy leader of the Democrats, after Natasha Stott Despoja toppled Meg Lees in a leadership spill.

He continued as deputy leader until August 2002, when along with fellow senators John Cherry, Meg Lees and Andrew Murray, he succeeded in forcing Stott Despoja to resign. It was widely tipped that he would succeed her as leader. However, the media did not portray the spill kindly, labelling them the 'Gang of Four'.

Ridgeway took over as interim leader, and nominated for the permanent leadership, being expected to win. At the last minute, Brian Greig lodged a nomination in protest at Ridgeway's treatment of Stott Despoja. In a surprise result, the majority of the party membership voted for Greig.

After his defeat in the 2002 leadership ballot, Ridgeway lost his position as deputy leader, being replaced by Lyn Allison. He remained in the Senate, being particularly active on issues of indigenous affairs and reconciliation. He lost his seat in the 2004 election, along with Cherry, Lees (who had since left the party), and Brian Greig, another Democrat senator. His term expires on 30 June, 2005.