A millionaire (originally and sometimes still millionnaire) is an individual whose net worth or wealth exceeds one million units of currency. It can also be a person who owns one million units of currency in a bank account or savings account. Depending on the currency, a certain level of prestige is associated with being a millionaire, which makes that amount of wealth a goal for some, and almost unattainable for others.

The increasing number of millionaires is partially due to prevailing economics: Increasingly, the term denotes more and more to the status of high wealth. American sociologist Leonard Beeghley classifies all households with net worth exceeding USD$1 million as "The Rich." Currently, there are over 10 million residents around the globe classified as U.S. dollar millionaires.

Terminology

The word was first used (as millionnaire, double "n") in French in 1719 by John Law, and is first recorded in English (millionaire, as a French term) in a letter of Lord Byron of 1816, then in print in Vivian Grey, a novel of 1826 by Benjamin Disraeli.{{cite web|url=http://dictionary.oed.com/cgi/entry/00309741?single=1&query_type=word&queryword=millionaire&first=1&max_to_show=10|title=Millionaire (n and adj)|work=Oxford English Dictionary|accessdate=2008-07-20|format=available online to subscribers but also available in print | quote=1816 BYRON Let. 23 June (1976) V. 80 He is still worth at least 50-000 pds{em}being what is called here Evian a ‘Millionaire' that is in Francs & such Lilliputian coinage. 1826 B. DISRAELI Vivian Grey I. ix, Were I the son of a Millionaire, or a noble, I might have all.}} An earlier English word "millionary" was used in 1786 by Thomas Jefferson while serving as Minister to France; he wrote: "The poorest labourer stood on equal ground with the wealthiest Millionary". The first American printed use of the word is thought to be in an obituary of New York tobacco manufacturer Pierre Lorillard II in 1843.

The increasing prevalence of people with more and more money has given rise to additional terms to further differentiate millionaires. A multimillionaire has a net worth of more than 2 million units of currency, a decamillionaire has a net worth of more than 10 million units of currency, and a hectomillionaire has a net worth of more than 100 million units of currency. The term centimillionaire has become synonymous with hectomillionaire in America, despite the centi- prefix meaning 1/100, not 100, in the metric system.

While statistics regarding financial assets and net worth are presented by household, the term is also often used to describe only the individual who has amassed the assets as millionaire. That is, even though the term statistically refers only to households, common usage is often in reference only to an individual.