Samantha Jane McMahon^[1] (born 11 December 1967) is a former Australian politician who was a Senator for the Northern Territory between the 2019 federal election and the 2022 federal election. McMahon is a member of the Liberal Democratic Party (LDP), having joined the party in April 2022, several months after resigning from the Country Liberal Party (CLP). While she was a CLP member, she sat in the Nationals party room in federal parliament. She was a veterinarian in Katherine before entering politics.^[2]

McMahon was born in Sydney on 11 December 1967.^[3] She grew up on a farm in Nanango, Queensland. She completed a Bachelor of Veterinary Science at the University of Queensland.^[4]

McMahon accepted a position in the Northern Territory after her graduation. She has owned and operated veterinary practices in Katherine,^[5] Howard Springs, Nhulunbuy, Tennant Creek, and Alice Springs. She was a national director of the Australian Veterinary Association for five years and president of the Northern Territory division for two years.^[4] She became a Fellow of the Australian Institute of Company Directors in 2003.^[6] She won the Centenary Medal for business leadership in 2001,^[7] was awarded the Australian Veterinary Association Meritorious Service Award in 2014,^[8] and was awarded the NT Telstra small business award in 2017.^[9]

In March 2019, McMahon won preselection to replace Nigel Scullion as the Country Liberal Party's lead Senate candidate at the 2019 federal election.^[10] She was elected to a term beginning on 18 May 2019,^[11] and chose to sit with the National Party in federal parliament, following her predecessor.^[12] In May 2021 she was appointed chair of the Joint Standing Committee on the National Capital and External Territories.^[3]

In June 2021, McMahon was defeated for CLP preselection at the 2022 federal election by Jacinta Price.^[13] In the week leading up to the ballot, Nine Publishing reported that at least ten senators believed she had been visibly drunk while in the Senate chamber on 23 June. A spokesman stated that she was feeling "unwell" and that the allegations were part of a smear campaign to discredit her in the lead-up to the preselection.^[14]

In December 2021 it was alleged that following a 'boozey' Christmas party McMahon was escorted from the premises to a waiting taxi, at which point McMahon physically assaulted Nationals federal director and event organiser Jonathan Hawkes. ^[15]

In January 2022, McMahon resigned from the Country Liberal Party and moved to the crossbench to sit as an independent.^[16] She later explained in March 2022 that she resigned due to alleged abuse by former staffer Jason Riley.^[17] On 8 April 2022, McMahon announced she had joined the Liberal Democrats, and would run on the party's Northern Territory Senate ticket at the May federal election.^[18][19] The Liberal Democrats won approximately 9% of the vote in the Northern Territory Senate race, not enough for McMahon to retain her seat in the chamber.

McMahon lives on a farm outside Katherine and is an avid water skier and horse rider.^[4] In September 2019, McMahon announced that she had separated from her husband, Wayne Nayda.^[25]