This comprehensive and comparative study examines the landscape of contemporary shareholder activism in the UK, focusing on minority shareholder activism in publicly listed companies. It argues that contemporary shareholder activism in the UK is dominated by two groups: the institutional shareholders whose shareholder activism is largely seen as a driving force for good corporate governance, and the hedge funds whose shareholder activism is based on value extraction and exit. The book provides a detailed examination of both types of shareholder activism, and critically discusses the nature of, motivations for, and consequences of following both types of shareholder activism. The book then locates both types of shareholder activism in the theory of the company and the fabric of company law, and argues that institutional shareholder activism based on exercising a voice at general meetings is well supported in theory and law. The call for institutions to engage in more informal forms of activism in the name of 'stewardship' may bring about challenges to the current patterns of activism that institutions engage in. The book argues, however, that a more cautious view of hedge fund activism and the pattern of value extraction and exit should be taken. More empirical evidence is likely to be necessary, however, to weigh up the long terms benefits and costs of hedge fund activism. It will be of interest to policy-makers, academics, and post-graduate students studying corporate governance and corporate law.