Nathan Rees (/riːz/; born 12 February 1968) is an Australian former politician who served as the 41st Premier of New South Wales and leader of the New South Wales Labor Party from September 2008 to December 2009. Rees was a Member of the New South Wales Legislative Assembly, representing Toongabbie for Labor from 2007 to 2015.

Rees replaced Morris Iemma as Premier and party leader on 5 September 2008. At 40 years and 206 days of age, Rees became the youngest person to assume the office, a record that has since been surpassed by Dominic Perrottet. On 3 December 2009, Rees was deposed as leader of the Labor Party by Kristina Keneally after he resoundingly lost a secret ballot in the Labor Party caucus after fifteen months as Premier. He is the shortest-serving member of the New South Wales Parliament to become Premier since Federation, and the only Labor Premier of New South Wales not to lead the party into an election. To date, he is also the most recent Australian state premier not to take his party into a general election.

Rees was born in 1968 in Western Sydney to parents Daryl and Frances, his mother being a longtime member of the Labor Party, reportedly from Penrith, New South Wales. He attended Northmead Creative and Performing Arts High School where he served as school captain. On leaving school he initially took up a horticultural apprenticeship and worked as a greenskeeper for Parramatta Council. Subsequently, he went on to study English literature at the University of Sydney, attaining an honours degree in 1994, supporting himself by working as a garbage collector at the same council. During his time at the Council he became Secretary of the then Municipal and Shire Employees Union.

Rees was a long-distance runner, and a member of the Parramatta Cycling Club, where he won many events. When training for races, Rees would cycle up to 1,000 km per week. He once attained third place in a state triathlon.

Rees's first job in politics was in 1995, when he became an adviser to the then deputy premier Andrew Refshauge, for whom his mother, Frances, worked. During this period, Rees cycled between Bullaburra in the Blue Mountains, where he lived at the time, and central Sydney, a distance of more than 90 km (56 mi).

He subsequently worked for Ministers Craig Knowles and Morris Iemma, and as chief of staff for Minister Milton Orkopoulos. Rees transferred to the Premier's office in 2006, three months before Orkopoulos was charged with child sexual abuse. Rees has stated that he had no knowledge of the crimes committed by Orkopoulos, and would have reported him to the police had he been aware of them.^{[dubious – discuss]}

Rees was elected to the New South Wales Legislative Assembly on 24 March 2007. He was almost immediately promoted to cabinet, becoming Minister for Emergency Services and Minister for Water Utilities on 2 April 2007.

As Minister for Water Utilities, Rees was responsible for implementing the $1.9 billion Sydney Desalination Plant at Kurnell, and the proposed Tillegra Dam in the Hunter Region.