Iwate 4th district is a constituency of the House of Representatives in the Diet of Japan (national legislature). It is located in southwestern Iwate and consists of the cities of Hanamaki, Kitakami and Ōshū as well as the Waga and Isawa Districts. As of 2012, 305,917 eligible voters were registered in the district. Before the electoral reform of 1994, the area had been part of Iwate 2nd district where three Representatives had been elected by single non-transferable vote.