LÉ Deirdre (P20) was a ship in the Irish Naval Service. She was named after Deirdre, a tragic heroine from Irish mythology who committed suicide after her lover's murder. Built in 1972, Deirdre was built as a replacement for the Ton-class minesweepers, and one of the first vessels custom-built for the Irish Naval Service. She was to have longer range and be a more seaworthy ship for work in the Atlantic. Deirdre became the prototype for the later -type vessels.