The city is named after the Iguaçu River that runs through it and empties into Guanabara Bay (not to be confused with the larger and better-known Iguaçu River in Paraná state, which forms the famous falls bearing its name). It is part of the Greater Rio de Janeiro metropolitan area. It was the state's second largest city in population until Mesquita was split off, and now it is the fourth largest behind São Gonçalo, Duque de Caxias and the state capital, Rio de Janeiro. It lies northwest of Rio de Janeiro, in the centre of the northern part of its metropolitan area, Baixada Fluminense. The current mayor is Nelson Bornier (PMDB). The city is the seat of the Roman Catholic Diocese of Nova Iguaçu.
Nova Iguaçu has an estimated population of around 800,000 people. Although not best defined as a commuter town, it is a suburb of Rio de Janeiro under the influence of the capital – to which tens of thousands of workers and students commute daily, or visit regularly for options in culture, entertainment, goods, health care, etc. It is a city of average, lower middle income. There are a few historical and ecotouristical attractions in the municipality.