IAH may refer to:

• George Bush Intercontinental Airport (IATA: IAH), an international airport in Houston, Texas
• Iah, a god of the moon in ancient Egyptian religion
• Iah (queen), a king's mother of ancient Egypt during the 11th dynasty
• International Association of Hydrogeologists, a scientific and educational organisation
• Workers International Relief , an adjunct of the Communist International
• I Am Hardwell, 2013/2014 world tour of Dutch DJ and Producer Hardwell. Also, the title of his 2013 documentary film.

Iah ( Egyptian: , transliterated as Yah, Jah, Jah(w), Joh or Aah ) is a god of the moon in ancient Egyptian religion. His name simply means moon. By the New Kingdom he was less prominent as a moon deity than the other gods with lunar connections, Thoth and Khonsu. As a result of the functional connection between them he could be identified with either of those deities.