LIR or Lir may refer to:

• Lir, sea god in Irish mythology
• Lir (band)
• Long Island Rail Road
• Local Internet Registry
• IATA airport code for Daniel Oduber Quirós International Airport in Costa Rica

Lir or Ler ("the sea") is a sea god in Irish mythology. His name suggests that he is a personification of the sea, rather than a distinct deity. He is named Allód in early genealogies, and corresponds to the Llyr of Welsh mythology. A further connection to Leir of Britain, most famous as William Shakespeare's King Lear, is possible but obscure. Like his Welsh counterpart Lir is chiefly an ancestor figure, and is best known as the father of the god Manannán mac Lir, who appears frequently in medieval Irish literature. Lir does have some prominence of his own; most famously the titular king in the tale The Children of Lir is named Lir.