H3, H03 or H-3 may refer to:

Entertainment

* '' Happy Hustle High'', a manga series by Rie Takada, originally titled "H3 School!" * ''H3'' (film), a 2001 film about the 1981 Irish hunger strike * h3h3Productions, styled " 3, a satirical YouTube channel

Science

* Triatomic hydrogen (H₃), an unstable molecule * Trihydrogen cation (H₃⁺), one of the most abundant ions in the universe * Tritium (Hydrogen-3, or H-3), an isotope of hydrogen * ATC code H03 ''Thyroid therapy'', a subgroup of the Anatomical Therapeutic Chemical Classification System *

British NVC community H3 NVC community H3 (''Ulex minor - Agrostis curtisii'' heath) is one of the heath communities in the British National Vegetation Classification system. It is one of three communities which are considered transitional between the lowland dry heaths a ...

, a heath community of the British National Vegetation Classification system * Histamine H₃ receptor, a human gene * Histone H3, a component of DNA higher structure in eukaryotic cells * , one of the three laryngeals in the reconstructed Proto-Indo-European language *

Hekla 3 eruption The Hekla 3 eruption (H-3) circa 1000 BC is considered the most severe eruption of Hekla during the Holocene. It threw about 7.3 km3 of volcanic rock into the atmosphere, placing its Volcanic Explosivity Index (VEI) at 5. This would have ca ...

, a huge volcanic eruption around 1000 BC

Computing

* , the level-3 HTML heading markup element * HTTP/3, the third revision of a protocol for the World Wide Web * Socket H3, the common name of the LGA 1150 CPU socket

Transportation

Air and space

* H3 (rocket), an expendable launch system under development by Japan Aerospace Exploration Agency * Harbour Air Seaplanes (IATA code), a Canadian charter airline * H-3 Air Base, former Iraqi Air Force base in western Iraq *

H-3 Sea King The Sikorsky SH-3 Sea King (company designation S-61) is an American twin-engined anti-submarine warfare (ASW) helicopter designed and built by Sikorsky Aircraft. A landmark design, it was one of the first ASW rotorcraft to use turboshaft engin ...

, a United States Navy helicopter * Standard H-3, an improved version of the 1916 Standard H-2 aircraft

Automobiles

* Brilliance H3, a Chinese compact sedan * Haval H3, a Chinese compact SUV *

Huansu H3 The Huansu H3 is a 7-seat MPV produced by Huansu, a brand of the Chonqing Bisu Automotive Corporation, which is closely related to Beiqi-Yinxiang, a joint venture between Beijing Auto (Beiqi) and the Yinxiang Group. Overview The Huansu H3 wa ...

, a Chinese compact MPV * Hummer H3, an American mid-size SUV

Ships

* USS ''H-3'' (SS-30), a 1914 United States Navy H-class submarine * HMS ''Grenville'' (H03), a 1935 British Royal Navy destroyer * HMS ''H3'', a 1915 British Royal Navy H-class submarine

Rail

* H3 series of METRORail tramways in Houston

Roads

* H3 Monks Way, a road part of the Milton Keynes grid road system, United Kingdom *

Interstate H-3 Interstate H-3 (abbreviated H-3) is an Interstate Highway located entirely within the U.S. state of Hawaii on the island of Oahu. H-3 is also known as the John A. Burns Freeway. It crosses the Ko'olau Range along several viaducts and through th ...

, a highway in Hawaii

Other uses

* H3 (classification), a para-cycling classification * H3, an 18th-century marine chronometer by John Harrison * H3, a type of automotive halogen lamp *

H3 (pyrotechnics) H3 is a pyrotechnic composition which is used mostly as a burst charge for small diameter shells. It is friction and shock sensitive, as are most compositions containing chlorates. For this reason, H3 should be mixed using the "diaper method" an ...

, a pyrotechnic composition * H3 Hardy Collaboration Architecture, a firm started by Hugh Hardy * H3 Pharmaceutical Chemistry, an advanced subject for GCE A-level students in Singapore * DSC-H3, a 2008 Sony Cyber-shot camera * Hash House Harriers, an international group of non-competitive running, social and drinking clubs * H3 (Kuwait), an archaeological site