IU may refer to:
The IUCN Red List of Threatened Species (also known as the IUCN Red List or Red Data List), founded in 1964, is the world's most comprehensive inventory of the global conservation status of biological species.
Lee Ji-eun (Korean: 이지은; born May 16, 1993), professionally known as IU (Korean: 아이유), is a South Korean singer-songwriter and actress.
In chemical nomenclature, the IUPAC nomenclature of organic chemistry is a systematic method of naming organic chemical compounds as recommended by the International Union of Pure and Applied Chemistry (IUPAC).
South Korean singer-songwriter IU has released four studio albums, nine extended plays (EPs), 43 singles (including 16 as featured artists), two single albums and 40 music videos.
On 29 January 2010, the IUCN Red List of Threatened Species identified 842 (746 animals, 96 plants) extinct species, subspecies and varieties, stocks and sub-populations.
The Indiana University of Pennsylvania Crimson Hawks, commonly known as the IUP Crimson Hawks and formerly called the IUP Indians, are the varsity athletic teams that represent Indiana University of Pennsylvania, which is located in Indiana, Pennsylvania.
The International Union of Pure and Applied Chemistry publishes many books, which contain its complete list of definitions.