Masterton (Maori: Te Oreore) is a large town and local government district in the Wellington Region of New Zealand. It is the largest town in the Wairarapa, a region separated from Wellington by the Rimutaka ranges. It is 100 kilometres north-east of Wellington, 28 kilometres south of Eketahuna, on the Ruamahanga River.

Masterton is a thriving community with an urban population of 20,200, and district population of 23,500 (June 2011 estimates).

The Wairarapa Line railway allows many residents easy access to work in the cities of Wellington, Lower Hutt and Upper Hutt.

Local industries involve service industries for the surrounding farming community. Industrial development is growing in Masterton, with three new industrial parks being developed in Waingawa, Solway and Upper Plain. The town is the headquarters of the annual Golden Shears sheep-shearing competition.

Despite the fact that Masterton is a town, not a city, it is still home to many suburbs. These include:

Named after pioneer Joseph Masters, Masterton was first settled by Europeans on 21 May 1854. It gained borough status in 1877. It did not quite qualify to be a city by 1989 when the minimum population requirement for that status was lifted from 20,000 to 50,000.

Graham Masterton (born 16 January 1946 in Edinburgh) is a British horror author. Originally editor of Mayfair and the British edition of Penthouse, Graham Masterton's first novel The Manitou was released in 1976. This novel was adapted in 1978 for the film The Manitou. Further works garnered critical acclaim, including a Special Edgar award by the Mystery Writers of America for Charnel House and a Silver Medal by the West Coast Review of Books for Mirror. He is also the only non-French winner of the prestigious Prix Julia Verlanger for his novel Family Portrait, an imaginative reworking of the Oscar Wilde novel The Picture of Dorian Gray. Masterton was also the editor of Scare Care, a horror anthology published for the benefit of abused children in Europe and the USA.

Masterton's novels often contain visceral sex and horror. In addition to his novels Masterton has written a number of sex instruction books, including How To Drive Your Man Wild In Bed and Wild Sex for New Lovers. A number of his novels have also been adapted into films.