LRN may refer to:
- Laboratory Response Network, a collaborative effort within the US federal government involving the Association of Public Health Laboratories and the Centers for Disease Control and Prevention
- Lateral reticular nucleus, a nucleus of the medulla oblongata involved with co-ordinating baroreceptor signals to control arterial blood pressure
- Legislative route number, a designation for a highway defined by laws passed in a state legislature
- Local Routing Number, a ten digit phone number used to route phone calls between two telephone exchanges
- LORAN, a terrestrial radio navigation system originally known as LRN for Loomis Radio Navigation
- LRNinc, a consulting company
- Luminous red nova, a stellar explosion thought to be caused by the merger of two stars