Seafarers were the first workers to inhabit a truly international labour market. They worked in an economic sector – the maritime one – which, throughout the early modern period, drove European economic and imperial expansion, technological and scientific development and cultural and material exchanges around the world. The period from the late sixteenth to the early nineteenth centuries was a time of economic and cultural transition, punctuated by crises, in which new emergent powers challenged the dominance of older centres, legal systems were reshaped by international interactions, and skilled labourers were subjected to the pressures of interconnecting and growing economies. Sailors were key protagonists throughout all of these developments, intertwined in the long and complicated process of globalisation. The cumulative actions of their myriad and diverse working lives are of pivotal importance to understanding this era and its consequences. Although frequently seen as homogeneous and powerless, seamen possessed a degree of individual agency which deserves to be recognised: to understand that agency, its limits and its consequences is the primary aim of this volume. Given the mobility of seafarers and the flexibility of their employment between different national domains, it is of crucial importance to adopt a comparative approach if we are to contemplate the workings of this global labour market, the actions of seamen within it and their ultimate impact. It is equally critical to reconcile the vast but practically faceless context of economic factors and legal codes in maritime trade with the experiences of individual people and communities. These two dimensions have sometimes been overlooked in historical research on seafarers, often written within a single national history or, when international comparisons are pursued, most regularly presented in broad statistical terms. Even beyond national histories, there has been a tendency to work within oceanic regions rather than to draw comparisons and connections between them, and more attention has been given to European sailors’ activities in the Atlantic and Indian Oceans than to seafaring in the Mediterranean, despite its continuing importance to the European economy and international politics, and the profound influence of Mediterranean traditions upon maritime practices elsewhere. Moreover, where research has explored the globalisation of European legal regimes and seafarers’ involvement in it, scholars have often focused on colonisation, piracy and war, while the customary and civil law apparatus through which the vast bulk of maritime trade was regulated has been neglected.