Old age - and particularly the increasing numbers of older people globally and within the United Kingdom - is becoming a social and political phenomenon. Yet despite this, very little has been written on how the law - and especially mental disability law - intersects with old age. This is notwithstanding the fact that many older people may encounter conditions that impact their mental or cognitive abilities, and proportionally, may therefore be greatly affected by this area of law.By drawing on a number of theories - sometimes termed 'relational' theories - which are derived predominantly from feminist theory, this thesis seeks to explore the adequacy of mental disability law for safeguarding health and welfare-related decision-making of older adults in three areas; where an older person has been subjected to ageism, where they have been the victim of interpersonal abuse, and where they have dementia and may lack mental capacity. Within this broader goal, this thesis has two specific aims. First, to explicitly critique and challenge the adequacy of the law as it is applied in these circumstances. It is suggested in particular that a deeper analysis of the law in both its previous and current forms betrays the liberal and unduly individualistic roots of the legislative framework. These are roots that are predicated on non-interference, and an idealistic paradigm of the rational, autonomous, and healthy bodied individual. This - it is contended throughout - is an unsuitable philosophy to underpin the law, particularly where the law engages with older adults.Second, this thesis aims to navigate a more suitable pathway within the law as it currently exists. While operating as a tool to critique the legislative framework and its underpinning philosophy, it is argued that the theories drawn upon throughout the thesis also have the potential to highlight how the law could be implemented in such a way so as to emphasise the importance of the realities of the lived experiences of old age, and particularly the experience of ageism, abuse, and dementia. Crucially, it is also suggested that such theories can help the law pay greater attention to the complex web of relationships - both positive and negative; personal and societal - that an older person may find themselves embedded within, and that frequently take on an added significance in old age.