Melissa Fay McMahon (born 15 May 1976) is an Australian politician. She has been the Labor member for Macalister in the Queensland Legislative Assembly since 2017.^[1] She is a member of the Parliamentary Crime and Corruption Committee (PCCC) and the Legal Affairs and Community Safety Committee (LACSC) of the Queensland Parliament.^[2]

Prior to her election to the Queensland Parliament, McMahon was a major in the Australian Army working in CIMIC, military police, information operations and career management. She served overseas in Timor-Leste in 2008 and 2011. She was also a senior sergeant in the Queensland Police Service, having worked on the Gold Coast, Logan and Brisbane.

McMahon has bachelor's degrees in behavioural science, policing and secondary education with a diploma of public safety and qualifications in training and education.

In the 2015 Queensland state election she ran in the seat of Albert, gaining a two-party-preferred swing of 10%, but lost to incumbent Mark Boothman.

McMahon is President of the Beenleigh Neighbourhood Centre. She has three children.