This dissertation examines the power that rumour held in England on the eve of the Civil Wars in relation to the Irish Rebellion and the ensuing massacres of 1641. Initially, it will consider how news of events across the Irish Sea arrived and spread across England in an uncontrolled manner. By considering contemporary accounts and pamphlet material it will be possible to see how these stories came to play a dominant role in the heated discussions taking place between Charles I and sections of Parliament at the time. This study investigates the effects this had upon the country as the Civil War period began. Looking at the various ‘panics’ that struck the country and the ways in which Charles I was seen to be complicit with an Irish Catholic invasion will enable an analysis of how Parliamentarian polemicists used the opportunity to undermine the monarch’s authority. Furthermore, it considers what it was that made the Irish so fearful in the eyes of the English populace and how Parliament was able to legitimise the ban on quarter for Irish soldiers, despite it clearly going against established Europe-wide codes of military conduct. Finally, this study scrutinizes the debates surrounding the 1649 re-conquest of Ireland and looks at how Oliver Cromwell was able to use memories of 1641 to justify the slaughter of nearly 5,000 men at Drogheda and Wexford. Ultimately, this dissertation suggests ways in which rumour was used to promote hatred and justify harsh political actions against the Irish and goes beyond the established notion that the Civil War was primarily about religion, by proposing that the conflict was also about ethnicity and identity.