This chapter explores the complex relationship between lamentation, masculinity, and heroic action in the Alliterative Morte Arthure. It demonstrates how the fourteenth-century poem’s earlier episodes distinguish between the contained grief that prompts heroic action and the debilitating grief which shocks and overwhelms: the fighting men’s laments for their fallen comrades are qualitatively different from the grief displayed by the widow after the Duchess, her foster-daughter, is raped and killed. However, this gendered model of male, moderate grief, and female, overwhelming grief, breaks down when Gawain, Arthur’s beloved nephew, is killed in battle. Arthur himself becomes the grief-stricken lamenter, displaying feminised behaviour that his knights view as both ineffectual and unseemly. The chapter argues that Arthur’s lament is not only a catalyst for revenge, but also marks a move away from indiscriminate conquest towards heroic action focused on justice and the restoration of order.