Aaron Ronald "Ron" Castan AM QC (29 October 1939 – 1999) was a barrister and human rights advocate. He played a leading role in some of Australia's more important cases, such as the Gove land rights case, Koowarta v Bjelke-Petersen and the Franklin Dam case. One of his most celebrated roles was that of senior counsel in the Mabo case, which abolished the doctrine of terra nullius and recognised Aboriginal land rights in Australian law for the first time. Castan spent 10 years preparing and arguing the case on behalf of Eddie Mabo, for which he received widespread acclaim.
He also played a leading role in the legislative discussions on Australian Native Title law throughout the 1990s, having devised the solution to the standoff in the Australian Senate over the Wik settlement. Additionally, he was a founder of the Victorian Aboriginal Legal Service.
Although he is most famous for his work in constitutional and human rights law, Castan was an expert in many areas of law. The Castan Centre for Human Rights Law at Monash University is named after him, where his daughter, Melissa Castan (herself a human rights scholar), is Deputy Director.
He died suddenly at age 59 due to a complication following surgery. After his death, tributes flowed from the legal and political community. Famously, after his death, he was described by Senator Aden Ridgeway as "the great white warrior against racism".