Indonesia - Wikipedia. Indonesia (/ ˌ ɪ n d ə ˈ n iː ʒ ə / ( listen) IN-də-NEE-zhə, /-z i ə /-zee-ə; Indonesian: ), [lacks stress] officially the Republic of Indonesia (Indonesian: Republik Indonesia [rɛpublik ɪndonesia]), [lacks stress] is a transcontinental unitary sovereign state located mainly in Southeast Asia, with some territories in Oceania.