Yamaguchi 4th district (山口県第4区 Yamaguchi-ken dai-yon-ku) is a single-member electoral district for the House of Representatives, the lower house of the National Diet of Japan. It is located in Western Yamaguchi and consists of the cities of Shimonoseki and Nagato. The seat was most recently held by former Prime Minister of Japan Shinzo Abe until his assassination in July 2022. As of September 2011, 266,456 voters were registered in the district, giving its voters well above average (347,878 voters per district) vote weight. Unlike many prefectures where the capital is also the most populous city, Yamaguchi's major city is Shimonoseki, located at the western tip of Honshū and adjacent to Kyushu island's Fukuoka-Kitakyūshū metropolitan area which lies just south across the Kanmon Straits.