Lizzie O'Neill was a Dublin woman who was abducted, fatally shot, and dumped at Ticknock, County Dublin, Ireland in an alleged revenge killing and act of vigilantism in June of 1925. The investigation was an early test for the newly established Irish Free State and its national police, the Garda Síochána, which eventually arrested and charged a Garda Superintendent and a rural physician with kidnapping and murder. Even though both men were acquitted, a plaque now stands in Ticknock marking the incident.