Niihama (新居浜市, Niihama-shi) is a city located in the eastern part of Ehime Prefecture, Japan. It has the third largest population in Ehime, behind the prefectural capital of Matsuyama and the recently expanded city of Imabari.
On August 31,2016, the city has an estimated population of 121,758 and a population density of 519.67 persons per km². The total area is 234.30 km².
Niihama was founded on November 3, 1937. It is famous for its Besshi copper mine as well as the annual Niihama Taiko Festival (also known as "The Man Festival", otokomatsuri 男祭り) that is the center of annual drunken and boisterous activity, drawing tourists from around the country to watch this festival.
Niihama is known for its local dialect, Niihama-ben.