OL may refer to:
An organic light-emitting diode (OLED) is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound that emits light in response to an electric current.
Oliver Cromwell (25 April 1599 – 3 September 1658) was an English military and political leader and later Lord Protector of the Commonwealth of England, Scotland, and Ireland.
Olivia Newton-John, AO, OBE (born 26 September 1948) is an English-Australian singer, songwriter, actress, entrepreneur and activist.
Olanzapine (originally branded Zyprexa) is an antipsychotic medication used to treat schizophrenia and bipolar disorder.
Old English (Ænglisc, Anglisc, Englisc) or Anglo-Saxon is the earliest historical form of the English language, spoken in England and southern and eastern Scotland in the early Middle Ages.
Old Norse was a North Germanic language that was spoken by inhabitants of Scandinavia and inhabitants of their overseas settlements during about the 9th to 13th centuries.
The olive, known by the botanical name Olea europaea, meaning "European olive", is a species of small tree in the family Oleaceae, found in the Mediterranean Basin from Portugal to the Levant, the Arabian Peninsula, and southern Asia as far east as China, as well as the Canary Islands and Réunion.