LDN may refer to:
Arts and media
- "LDN" (song), a 2006 single by Lily Allen
- London Daily News, former newspaper
- BBC London (formerly BBC LDN), broadcasting body
Language
- Láadan, a feminist, sci-fi conlang (ISO 639-3:<code>ldn</code>)
Medicine
- Low-dose naltrexone, to treat immune diseases
- Licensed dietitian nutritionist, a qualified dietician
Places
- Lamidanda Airport, Nepal (IATA code)
- Lanao del Norte, province in Northern Mindanao, Philippines
- London, in British contractional slang
- Llandanwg railway station, north Wales (GBR:<code>LDN</code>)
Science and technology
- Day-night average sound level (Ldn)
- Linked Data Notifications, a communications protocol
- Lynds' Catalogue of Dark Nebulae, in astronomy