Oiolairë was a fragrant evergreen tree of Númenor.
The leaves of this tree were glossy as well as fragrant and trove off of the sea-air of the coasts, and were mainly to be found in the western region of Nísimaldar which surrounded the coastal city of Eldalondë. The Númenorians set it on their ships as a token of friendship to Ossë and Uinen.
The tree originated on the island of Tol Eressëa and was one of a host of Fragrant Trees brought to Númenor by the elves there as gifts of enrichment. Later when the Númenórean mariners began building a fleet of ships to explore the world, it had become the custom for female relatives of the mariners to place a bough of it on the prows of their ships. This bough became known as the Green Bough of Return.
The term Oiolairë means "Ever-summer", possibly from oia ("everlasting") and lairë ("summer").