Hara Takashi ( , 15 March 1856 4 November 1921) was a Japanese politician who served as the Prime Minister of Japan from 1918 to 1921.

Hara held several minor ambassadorial roles before rising through the ranks of the Rikken Seiykai and being elected to the House of Representatives. Hara served as Home Minister in several cabinets under Saionji Kinmochi and Yamamoto Gonnohye between 1906 and 1913. Hara was appointed Prime Minister following the Rice Riots of 1918 and positioned himself as a moderate, participating in the Paris Peace Conference, founding the League of Nations, and relaxing oppressive policies in Japanese Korea. Hara's premiership oversaw the Siberian intervention and the March 1st Movement. Hara was assassinated by Nakaoka Kon'ichi on 4 November 1921.

Hara was the first commoner and first Christian appointed to be Prime Minister of Japan, informally known as Hara Kei, and given the moniker of "commoner prime minister" (, heimin saish).

The prime minister of Japan (日本国内閣総理大臣, Nihon-koku naikaku sōridaijin, or shushō (首相)) (informally referred to as the PMOJ) is the head of the executive branch of the government of Japan. The prime minister directs the National Cabinet and is the commander-in-chief of the Japan Self-Defense Forces; he is appointed by the emperor of Japan after being designated by the National Diet and must enjoy the confidence of the House of Representatives to remain in office. He is the head of the Cabinet and appoints and dismisses the other ministers of state. The literal translation of the Japanese name for the office is Minister for the Comprehensive Administration of (or the Presidency over) the Cabinet.

The current prime minister of Japan is Fumio Kishida, who replaced Yoshihide Suga on 4 October 2021.