Kumamoto 4th District (熊本県第4区, Kumamoto-ken dai-yon-ku, or 熊本4区 Kumamoto yon-ku) is a current single-member electoral district for the House of Representatives, the lower house of the National Diet of Japan.

[2] Before 2013, it consisted of a small section of the prefectural capital Kumamoto (the former towns of Tomiai and Jōnan in today's Minami-ku), the cities of Amakusa, Uto, Kami-Amakusa and Uki and the remaining towns and villages of the former Amakusa, Upper (Kami-Mashiki) and Lower Mashiki (Shimo-Mashiki) counties.

Representatives had included Sunao Sonoda (DPJ→PDP→Progressive→JDP→LDP, 1947–1984) and his son Hiroyuki (LDP→NPH, 1986–1996).

Hiroyuki Sonoda, deputy chief cabinet secretary during the LDP-JSP-NPH coalition, won the new single-member 4th district six times in a row after the electoral reform.

Sonoda's main challenger in 2012, Masayoshi Yagami, had become a Liberal Democrat (JNP→NFP→LDP) when he represented the neighbouring 5th district in the 1990s, but became an independent for his two terms as mayor of Sagara and his failed run for governor of Kumamoto in 2008.