Mark Alfred Dreyfus KC (born 3 October 1956) is an Australian politician and lawyer. He is a member of the Australian Labor Party (ALP), and has been the MP for Isaacs since the 2007 election. Dreyfus served as the attorney-general of Australia in 2013 and then 2022 to 2025, and as cabinet secretary from 2010 to 2013 and then 2022 to 2025.

Before beginning his political career, Dreyfus worked as a barrister for two decades, specialising in constitutional, commercial and environmental law. After winning the seat of Isaacs in 2007, Dreyfus was appointed to the Cabinet in September 2010 by Julia Gillard as Cabinet Secretary. In February 2013, following the resignation of Nicola Roxon, he was moved to become Attorney-General for the first time. After Kevin Rudd replaced Gillard as Prime Minister in June 2013, Dreyfus was retained as Attorney-General and given the additional roles of Special Minister of State and Minister for the Public Service and Integrity. He would hold these positions for less than three months, as Labor was defeated in the 2013 election.

Throughout Labor's subsequent nine years in opposition, Dreyfus served as shadow attorney-general under both Bill Shorten and Anthony Albanese. Following Labor's victory in the 2022 election, he was appointed to the positions of Attorney-General and Cabinet Secretary for the second time within the first Albanese ministry. During his second tenure as attorney-general, he oversaw the introduction of the National Anti-Corruption Commission, the creation of the Administrative Review Tribunal in place of the abolished Administrative Appeals Tribunal, and the establishment of the Royal Commission into the Robodebt Scheme. He also ordered the discontinuation of the prosecution of whistleblower Bernard Collaery. He was removed as attorney-general following a cabinet reshuffle after the 2025 election.

Dreyfus was born in Perth, Western Australia, the son of George Dreyfus, a noted composer who came to Australia from Nazi Germany. Three of Mark's great-grandparents perished during The Holocaust. Mark's father was moved to Australia when he was eleven years old. Many Jewish children in Australia were cared for throughout the war, including Mark's father, who had no idea if they would ever see their parents again. Dreyfus was educated at Scotch College, Melbourne on a full scholarship and the University of Melbourne, where he resided at Ormond College and graduated with a Bachelor of Arts and a Bachelor of Laws.

Before entering parliament, Dreyfus worked as a barrister for twenty years, with an extensive practice in commercial, defamation, constitutional and environmental law. He appeared before the High Court in the leading implied freedom of political communication cases of Theophanous v Herald & Weekly Times Ltd (1994) and Lange v Australian Broadcasting Corporation (1997). He also represented Michael Danby in a defamation suit against the LaRouche movement. In 1999 he was appointed Queen's Counsel.

Dreyfus also served as a director of the Law Council of Australia and on the Victorian Bar Council and Victorian Bar Ethics Committee.

Since his first professional role as a Field Officer for the Northern Land Council, Dreyfus has worked closely with Aboriginal communities in the Northern Territory, including representing a number of the claimants in the landmark Stolen Generations litigation.

In March 2006, Dreyfus successfully challenged the sitting Labor member for the Division of Isaacs, Ann Corcoran, for the Labor candidacy in the 2007 election. At the 2007 election, he defeated the Liberal candidate, Ross Fox, gaining a 5.9-point swing to Labor.