1921 in Japan

Events from the year 1921 in Japan. It corresponds to Taishō 10 (大正10年) in the Japanese calendar.

Incumbents

 * Emperor: Taishō
 * Regent: Hirohito (from November 25)
 * Prime Minister:
 * Hara Takashi (until November 4)
 * Takahashi Korekiyo (from November 13)

Governors

 * Aichi Prefecture: Shunji Miyao (until 18 April); Hikoji Kawaguchi (starting 18 April)
 * Akita Prefecture: Ryoshin Nao
 * Aomori Prefecture:
 * until 9 March: Hidehiko Michioka
 * 9 March-28 September: Shundo Kahei
 * starting 28 September: Yujiro Ozaki
 * Ehime Prefecture: Toshio Mawatari (until 27 May); Juunosuke Miyazaki (starting 27 May)
 * Fukui Prefecture: Kohei Yuji (until 27 May); Josuke Shiraogawa (starting 27 May)
 * Fukuoka Prefecture: Yasukouchi Asakichi
 * Fukushima Prefecture: Miyata Mitsuo
 * Gifu Prefecture: Kanokogi Kogoro (until 27 May); Manpei Ueda (starting 27 May)
 * Gunma Prefecture: Muneyoshi Oshiba
 * Hiroshima Prefecture: Raizo Wakabayashi (until 19 July); Ichiro Yoda (starting 19 July)
 * Ibaraki Prefecture: Yuichiro Chikaraishi (until 27 May); Genjiro Moriya (starting 27 May)
 * Iwate Prefecture: Takeo Kakinuma
 * Kagawa Prefecture: Yoshibumi Satake
 * Kochi Prefecture: Abe Yoshihiko
 * Kumamoto Prefecture: Hikoji Kawaguchi (until 27 May); Sansuke Nakayama (starting 27 May)
 * Kyoto Prefecture: Eitaro Mabuchi (until July); Raizo Wakabayashi (starting July)
 * Mie Prefecture: Haruki Yamawaki
 * Miyagi Prefecture: Mori Masataka (until 27 May); Yuichiro Chikaraishi (starting 27 May)
 * Miyazaki Prefecture: Naomiki Hirose (until 3 July); Goro Sugiyama (starting 3 July)
 * Nagano Prefecture: Tenta Akaboshi (until 27 May); Tadahiko Okada (starting 27 May)
 * Niigata Prefecture: Ota Masahiro
 * Okayama Prefecture: Masao Kishimoto
 * Okinawa Prefecture: Sōsuke Kawagoe (until 27 May); Jyun Wada (starting 27 May)
 * Saga Prefecture: Sawada Ushimaro (until 3 June); Tominaga (starting 3 June)
 * Saitama Prefecture: Horiuchi Hidetaro
 * Shiname Prefecture: Sanehide Takarabe
 * Tochigi Prefecture: Hiroyoshi Hiratsuka
 * Tokushima Prefecture: Rinpei Otsu (until month unknown)
 * Tokyo: Hiroshi Abe (until 27 May); Katsuo Usami (starting 27 May)
 * Toyama Prefecture: Higashizono Motomitsu (until 24 December); Shida Jisho (starting 24 December)
 * Yamagata Prefecture: Ichiro Yoda (until 19 July); Morimoto Izumi (starting 19 July)
 * Yamanashi Prefecture: Miki Nagano

Events

 * January 15 – Mitsubishi Electronics was separate section from Mitsubishi Shipbuildings (now Mitsubishi Heavy Industries) which was founded in Ōsone, Nagoya.
 * January Unknown date – Komatsu Limited was founded, as predecessor name was Komatsu Ironworks.
 * September – Sempill Mission sent by Britain to Japan, with the objective of helping the Imperial Japanese Navy develop its aeronaval forces.
 * October 16 – Janome Sewing Machine founded.
 * November 4 – Prime Minister Hara Takashi is assassinated at Tokyo Station.
 * November 12 – Washington Naval Conference opens at Memorial Continental Hall Hall in downtown Washington DC.
 * November 25 – Crown Prince Hirohito is made regent in place of his ailing father.
 * December 13 – In the Four-Power Treaty on Insular Possessions, Japan, the United States, United Kingdom, and France agree to recognize the status quo in the Pacific.
 * Termination of Anglo-Japanese Alliance.
 * Ladies' Agreement
 * Unknown date – Otsuka Pharmaceutical (大塚製薬) founded in Naruto, Shikoku Island.

Births

 * January 3 – Natsuko Kahara, actress (d. 1991)
 * January 26 – Akio Morita, businessman and co-founder of Sony Corporation (d. 1999)
 * February 9 – Junzo Shono, writer (d. 2009)
 * February 11 – Edward Seidensticker, scholar, historian, and translator (d. 2007)
 * February 14 – Toshiko Taira, textile artist (d. 2022)
 * March 19 – Heitaro Nakajima, engineer (d. 2017)
 * April 20 – Michiko Inukai, writer and philanthropist (d. 2017)
 * December 20 – Kosuke Gomi, novelist (d. 1980)

Deaths

 * January 13 – Ijuin Gorō, admiral (b. 1852)
 * June 19 – Nabeshima Naohiro, politician and former daimyō (b. 1846)
 * September 28 – Yasuda Zenjirō, entrepreneur, founder of the Yasuda zaibatsu (b. 1838)
 * November 4 – Hara Takashi, Prime Minister of Japan (b. 1856)
 * November 5 – Yusuke Hashiba, archaeologist, historian and anthropologist (b. 1851)
 * December 29 – Hayashi Yūzō, politician (b. 1842)