A millionaire is an individual whose net worth or wealth is equal to or exceeds one million units of currency. Depending on the currency, a certain level of prestige is associated with being a millionaire.[2] Many national currencies have, or have had at various times, a low unit value, in many cases due to past inflation. It is much easier and less significant to be a millionaire in those currencies, thus a millionaire in the local currency of Hong Kong or Taiwan, for example, may be merely of average wealth, or perhaps less wealthy than average. A millionaire in Zimbabwe in 2007 could have been extremely poor.[3] Because of this, the term 'millionaire' generally refers to those whose assets total at least one million units of a high-value currency, such as the United States dollar, euro, or pound sterling.
At the end of 2011, there were around 5.1 million HNWIs in the United States,[4] while at the same time there were 11 million millionaires[5] in a total of 3.5 million millionaire households,[6] including those 5.1 million HNWIs. As of December 2023[update], there were estimated to be just over 16 million dollar-millionaires in the world according to the World's Wealthiest Cities Report 2024 by Henley & Partners. The United States had the highest number of millionaires (5.5 million) of any country, whilst New York is the wealthiest city with 349,500 millionaires.[7] In countries that use the short scale number naming system, a billionaire is someone who has at least a thousand times a million dollars, euros or pounds.