1921 in Japan

Incumbents

• Emperor: Taishō
• Regent: Hirohito
• Prime Minister:
• *Hara Takashi
• *Takahashi Korekiyo

  Events

• January 15 - Mitsubishi Electronics was separate section from Mitsubishi Shipbuildings 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 founded in Naruto, Shikoku Island.

  Births

• January 3 - Natsuko Kahara, actress
• January 26 - Akio Morita, businessman and co-founder of Sony Corporation
• February 9 - Junzo Shono, writer
• February 11 - Edward Seidensticker, scholar, historian, and translator
• March 19 - Heitaro Nakajima, engineer
• April 20 - Michiko Inukai, writer and philanthropist
• December 20 - Kosuke Gomi, novelist

  Deaths

• January 13 - Ijuin Gorō, admiral
• June 19 - Nabeshima Naohiro, politician and former daimyō
• September 28 - Yasuda Zenjirō, entrepreneur, founder of the Yasuda zaibatsu
• November 4 - Hara Takashi, Prime Minister of Japan
• November 5 - Yusuke Hashiba, archaeologist, historian and anthropologist
• December 29 - Hayashi Yūzō, politician