This is a study of mna caointe, Irish keening women. Ranging from the semi-professional to the more occasional, mna caointe performed the caoineadh (Irish women's lament) at wakes and funerals and led their communities in the public expression of grief. Their performances included extemporaneously composed, sung, oral elegiac poetry, interspersed with choruses of wailing cries. In addition to praising the deceased, mourning his/her passing, and aggressively criticizing his/her enemies, mna caointe articulated their own concerns and assorted social tensions. Mna caointe grieved incidents of domestic violence and social slights and cursed those who offended them. The practice of the caoineadh originated prior to the Christian period in Ireland and ceased in the early twentieth century. Employing a multitude of diverse source material, this study relies most heavily upon folklore manuscripts held by the Department of Irish Folklore at the National University of Ireland, Dublin in Belfield. Unlike the works of scholars of folklore, music, and literature that have preceded, this study examines mna caointe to better understand the dynamics of colonialism and community and to elucidate moments of innovation involving women and understandings of identity, death, and power. This work chronicles the religious and historical significance of mna caointe, from the medieval period through the twentieth century Irish Diaspora, by contextualizing the practice and performers, in various cultural settings. Throughout these periods, keening and mna caointe were central to both positive and pejorative definitions of "Irish" identity. In medieval mythology, keening was one of the ways otherworldly women demonstrated the intimate connection between the land and those who resided upon it. In the colonial era, British colonists and travel writers cited the caoineadh and mna caointe among the elements that made Irish culture inferior. In the eighteenth and nineteenth centuries, aware of colonizers' disdain, agrarian agitators, Eileen O'Connell (the most famous keening woman), and Daniel O'Connell resorted to folk traditions centered on allegorical women and keening to protest British ascendancy, as well as political and economic injustice. Through their performances, nineteenth century mna caointe managed grief for their communities, mediated between the living and the dead, effected the transfer of the deceased to the afterlife by impersonating supernatural females, and provided women and colonized Irish with tools to rhetorically resist domination. Though economically marginal, for much of the nineteenth century, skilled mna caointe were compensated in ways that demonstrated their value and importance to rural communities. Demographic changes that began before the mid-nineteenth century Irish Potato Famine and accelerated after, especially the rise of strong farmers and the decimation of the laboring poor, resulted in the slow and uneven decline in hiring mna caointe. While Catholic priests and Roman devotions usurped many of their functions, and religious and cultural underpinnings of the caoineadh deteriorated, folk traditions regarding the mediatory role of longhaired mourning women persisted into the twentieth century Irish Diaspora. The legacy of mna caointe can be found in how the Irish ritualized emigration, conceived transatlantic identity, redefined community, and understood the bean si (banshee, i.e. the Irish supernatural death messenger). In sum, Irish history and culture are more fully understood through an examination of mna caointe. Their mythological heritage, religious significance, and legacy demonstrate ways that largely disenfranchised Irish women employed understandings of the transcendent to shape, protest, and change their lives.