LÉ Emer (P21) of the Irish Naval Service, now known as NNS Prosperity of the Nigerian Navy, was built as a patrol vessel in Verolme Dockyard, Cork, Ireland in 1977.

[1] After evaluating Deirdre for 3 years, Emer was ordered by the Irish Naval Service in 1975.

Commissioned in January 1978, she was named after Emer, the principal wife of Cúchulainn, a legendary Irish folk hero.

[2] Decommissioned on 20 September 2013,[3] in October 2013 Emer was sold at auction for €320,000 to a Nigerian businessman.

[5] On 19 February 2015 Emer was commissioned into the Nigerian Navy as a training ship and renamed NNS Prosperity.