The idea of toxic masculinity might feel like a very modern, even twenty-first-century notion, but similar concerns about male behaviour, also often characterised in terms of poisons and poisoning, can be identified in the literature of four hundred years ago, not only in Shakespeare’s Othello and The Winter’s Tale but also lesser-known plays that were popular on the London stage in the 1600s. Poison-related tropes, and the recurrent plot device of a man trying to poison a woman, expressed complex and sometimes contradictory attitudes towards socially unacceptable male behaviour. These plays depict the early modern male as both poisoned and poisoner – poisoned by inherited misogynistic ideas and attitudes, and poisoner of women both literally and metaphorically. Seeing them as enacting problematic situations and raising difficult questions rather than simply offering the moral certitudes of Christianity or the prescriptions of contemporary conduct book, the book points to these plays as evidence of disquiet and anxieties to which we can still easily relate today. The fact that some plays responded to real life events such as familicide is an indicator of this socially responsible role of the theatre, engaging its audience in current issues and controversies. The use of the poison theme in relation to male violence and misogyny shows that the early modern theatre was engaging with such intractable problems in ways that are still thought-provoking today.