During the early decades of the early 17th century, the Stuart crown trebled the number of Irish peers. With this inflation of honours, itself an exercise in social engineering, the monarch created a peerage – a service élite – that comprised, in roughly equal numbers, catholic and protestant lords. Land, inherited through the practice of primogeniture, provided the income that sustained these lineages. As landlords, developers, entrepreneurs, politicians and military commanders, these lords operated as regional and national powerbrokers, exercising influence in Ireland and beyond. From the crown's perspective, the peers served as effective instruments in its efforts to ‘civilise’ and anglicize a particularly troublesome colony. This article provides a brief introduction to the role that Irish aristocrats played in shaping 17th century Ireland. It also situates the study of these Irish lords in the wider context of noble studies and reflects on why Irish historians have not examined the aristocracy as a collective. Finally, this article seeks to draw out some comparisons between the aristocracy in Ireland and their counterparts in the composite monarchies of Britain, Spain and Austria. The fact that during these years Ireland, like other states across early modern Europe, was responding to similar sets of pressures – state formation, confessionalisation, the professionalisation of warfare and so on – facilitate meaningful comparisons around the contributions that their aristocracies made to these transformative processes.