Arapuni is a rural town centre on the Waikato river in the South Waikato District of New Zealand. The population on census night 2006 was 2,145 usual residents, slightly down from 2,163 in 2001 and 2,211 in 1996. The town sits next to a hydroelectric dam at Lake Arapuni, one of six in the South Waikato District on the Waikato river.