- For 'freshwater scampi' in India, see Macrobrachium rosenbergii.
Scampi is a culinary name for a kind of small lobster known as Nephrops norvegicus, Norway lobster, Dublin Bay prawn, langoustine or "true scampi". The name is often used to loosely describe a style of preparation typical for this lobster.
Monkfish tail is sometimes illegally used and sold as scampi. In the UK this contravenes the Fish Labelling (Amendment) England Regulation 2005 and Schedule 1 of the Food Labelling Regulations 1996.
Scampi was made popular in the 1960s by the British company, Young's Seafood, who were asked by their white-fish trawlermen to find a use for langoustines, a by-catch from fishing in Lerwick, Lossiemouth and Annan in Scotland. Their Italian product development chef came up with the ubiquitous "Scampi in a Basket", which became the ultimate pub meal in the 1960s and 70s
Nephrops norvegicus 
Langoustines or Norway lobsters – Nephrops norvegicus – are roughly the size of a large crayfish and fished from silty bottom regions of the open Atlantic Ocean, and parts of the Mediterranean. The fleshy tail of the Norway lobster is closer in both taste and texture to lobster and crayfish rather than prawn or shrimp.
They are often informally known as Dublin Bay prawns, though the term "prawn" can be confusing since it is sometimes used to describe several varieties of shellfish: the first group includes members of the lobster family such as scampi (langoustine in French and cigala in Spanish), while the second takes in large shrimp, particularly those that live in fresh water. However, in terms of biological classification, lobsters like scampi are of a different family from prawns/shrimp.
The name is used loosely both in Italy and elsewhere to refer to other similar species, though some food labelling laws (in Britain, for example) define "scampi" as Nephrops norvegicus.
Preparation methods 
According to Larousse Gastronomique, langoustine are delicate and need to be poached only for a few seconds in court-bouillon. When very fresh they have a slightly sweet flavour which is lost when they are frozen. They can be eaten plain, accompanied by melted butter.
In Britain the shelled tail meat is generally referred to as "scampi" or "wholetail scampi", although cheaper "re-formed scampi" can contain other parts together with other fish. It is served fried in batter or breadcrumbs and usually with chips (french fries) and tartare sauce. It is widely available in supermarkets and restaurants, considered pub or snack food but its prevalence has reduced due to declining fish stocks.
In the USA, "scampi" is often the menu name for shrimp in Italian-American cuisine (the actual word for "shrimp" in Italian is gambero or gamberetto, plural gamberi or gamberetti). The term "scampi", by itself, is also the name of a dish of shrimp served in garlic butter and dry white wine, served either with bread, or over pasta or rice, although sometimes just the shrimp alone. Most variants of the "shrimp scampi" come on pasta. The word "scampi" is often construed as that style of preparation rather than an ingredient, with that preparation being called "shrimp scampi", and with variants such as "chicken scampi".
As an alternative seafood 
Owing to the decline of fish stocks, chefs including Heston Blumenthal and Hugh Fearnley-Whittingstall are attempting to raise awareness of alternative seafoods, by championing scampi  and other lesser-known seafood dishes as a more sustainable sources of protein.
- Online Etymological Dictionary s.v. scampi
- UK fish labelling regulations
- "Scampi shortage means popular pub snack could be off the menu this summer". Daily Mail. 13 June 2011. Retrieved 28 December 2011.
- Reynolds, Barbara. The Concise Cambridge Italian Dictionary, Cambridge University Press, 1975