THH

THH may refer to:


 * Hillingdon Hospital, west London, England (opened 1838)
 * Tetrahydroharmine, a fluorescent alkaloid chemical
 * Thomas Henry Huxley (1825–1895), English biologist
 * The Helping Hand (halfway house), a rehab in Singapore
 * Topological Hochschild homology, in abstract algebra
 * The Haunted House (anime), a South Korean TV series (2016–2024)