OL may refer to:
Oliver Cromwell (25 April 1599 – 3 September 1658) was an English military and political leader. He served as Lord Protector of the Commonwealth of England, Scotland, and Ireland from 1653 until his death, acting simultaneously as head of state and head of government of the new republic.
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.
Olanzapine (originally branded Zyprexa) is an antipsychotic medication used to treat schizophrenia and bipolar disorder.
Olivia Newton-John, (born 26 September 1948) is an English-Australian singer, songwriter, actress, entrepreneur, and activist.
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.
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.