These are the most deluxe St. Patrick's Day tiaras we carry! The IRFU, Shamrock Rovers FC, Aer Lingus, IDA Ireland, University College Dublin, University of Notre Dame, the Northern Ireland Tourist Board and Fáilte Ireland use the shamrock as part of their identity. Legend says that it was used by Saint Patrick to illustrate the doctrine of the Trinity, and it has become an emblem of Ireland (no official status in Northern Ireland or the Republic of Ireland).