Sheelah’s Day, observed every March 18, is a folk holiday celebrated primarily by the Irish diaspora in Canada and Australia. This day follows St. Patrick’s Day and is dedicated to Sheelah, who is believed to be the wife or mother of St. Patrick, the patron saint of Ireland. Although no longer officially recognized in Ireland, the holiday has historical roots in Irish folklore, with references to Sheelah appearing in 18th and 19th-century Irish journals. Celebrations often involve the consumption of alcohol, a tradition noted in 19th-century Australian press. In Newfoundland and Labrador, Canada, Sheelah’s Day is linked to the legend of Sheila NeGeira, an Irish princess who married Gilbert Pike, an early settler. The holiday may also have connections to sheela na gigs, medieval carvings thought to protect against evil spirits. Overall, Sheelah’s Day reflects a blend of Irish cultural heritage and folklore.