Irregular migration policies differ across western nations, nevertheless, a practice almost all have in common is the use of immigration detention. The detention facilities are intended to deter, manage, and deport unauthorised arrivals. Australia’s approach to immigration detention has been unique compared to other countries for two main reasons. Firstly, in recent decades Australia has utilised long-term, indefinite detention rather than holding people in immigration detention facilities for the shortest time possible. The amount of time people are held within these facilities by the Australian government has increased considerably over the past decade from an average of 81 days in 2013 to 689 days in 2021. Second, Australia’s use of offshore detention facilities in the Republic of Nauru and Manus Island to house detainees has been exceptional, though other countries such as the United Kingdom recently appear to be adopting this approach too. The rising use of mandatory immigration detention by western nations such as Australia is a controversial topic. Over the past decade, this has been highlighted by media reports, public debate and a growing body of research criticising this policy approach (particularly the length of detention and conditions to which detainees are subject). Current literature details the prevalence of a range of wellbeing issues that detainees experience, either because of or which are exacerbated by their detention in these facilities. Despite the problems of immigration detention being widely recognised, the practice persists. Most of the previous research concerned with the experience of immigration detention focuses on the general immigration detention population, which mainly consists of men. The aim of this thesis was to address the existing gap in the literature by focusing on the experiences of women held in long-term immigration detention in Australia. The research broadly asks what impact long-term immigration detention has on women’s physical, mental, and social wellbeing. Crewe's (2015) framework, which conceptualises the experiences of prisoners and detainees, guided the data collection and analysis with its four dimensions of depth, weight, tightness, and breadth of detention conditions.