Baron Wakatsuki Reijirō (若槻 禮次郎, 21 March 1866 – 20 November 1949) was a Japanese politician and Prime Minister of Japan.

Wakatsuki Reijirō was born on 21 March 1866, in Matsue, Izumo Province (present day Shimane Prefecture), the second son of samurai foot soldier (ashigaru) Okumura Sensaburō and his wife Kura.

In 1883, he decided to enter the Imperial Japanese Army Academy as the tuition fees were government expensed, but failed the physical examination.

The next year, he heard about student recruitment by the Law School of the Ministry of Justice, which also had its tuition fees covered by the government.

After serving as chief delegate plenipotentiary to the London Naval Conference 1930, Wakatsuki pushed strongly for speedy ratification of the disarmament treaty, thus earning the wrath of the Japanese military and various ultranationalist groups.

After Prime Minister Hamaguchi was forced out of office by the severe injuries incurred in an assassination attempt, Wakatsuki assumed the leadership of the Rikken Minseitō, the successor to the Kenseikai.

In May 1945, on hearing of the collapse of Nazi Germany, he emerged from retirement to urge Prime Minister Kantarō Suzuki to open negotiations with the United States as soon as possible.

After the surrender of Japan, Wakatsuki was subpoenaed by the Supreme Commander of the Allied Powers in June 1946 as a prosecution witness at The International Military Tribunal for the Far East.