Gunma 1st district is a constituency of the House of Representatives in the Diet of Japan (national legislature). It is located in Gunma Prefecture and consists of the cities of Maebashi, Numata, parts of Kiryū and Shibukawa as well as the Seta and Tone districts. As of 2012, 387,120 eligible voters were registered in the district.
Until 2009, Gunma had been a traditional "conservative kingdom" (hoshu-ōkoku), the Japanese equivalent of a "red state" in the United States. Like all single member districts in Gunma, the 1st district had been represented by the Liberal Democratic Party (LDP) since 1997. The LDP used the Costa Rica method (kosutarika-hōshiki) with Koji Omi and Genichiro Sata as alternating candidates for the district. In the election of 2009, Omi was the LDP's candidate; incumbent Sata only ran in the Northern Kantō proportional representation block. Both Omi and Sata had represented the pre-reform three-member 1st district of Gunma. The Democratic Party's candidate in 2009 was Takeshi Miyazaki, a former journalist for the Jōmō Shimbun. In 2012, Sata regained the district for the LDP.