Harukazu Nagaoka (長岡 春一, Nagaoka Harukazu, January 16, 1877 in Kobe, Japan – June 30, 1949) was a Japanese diplomat and jurist who served as member of the Japanese delegation to the Commission of Responsibilities at the Paris Peace Conference and represented Japan to the League of Nations. He also sat on a number of national and international judicial and arbitral positions, including as a judge on the Permanent Court of International Justice.