Masahito, Prince Hitachi (常陸宮正仁親王, Hitachi-no-miya Masahito Shinnō, born 28 November 1935) is a member of the Imperial House of Japan and the younger brother of Emperor Akihito. He is the second son and sixth born child of Emperor Shōwa and Empress Kōjun and is fourth in line to the Chrysanthemum Throne. Prince Hitachi is mainly known for philanthropic activities and his research on the causes of cancer.

Born at Tokyo Imperial Palace in Tokyo, Prince Masahito held the childhood appellation Prince Yoshi (義宮正仁親王, Yoshi-no-miya Masahito Shinnō).

He received his primary and secondary schooling at the Gakushūin Peers' School. In late 1944, the Imperial Household Ministry evacuated Prince Yoshi and the Crown Prince to Nikkō, to escape the American bombing of Tokyo.

After the war, from 1947 to 1950, Mrs. Elizabeth Gray Vining tutored both princes and their sisters, the Princesses Kazuko, Atsuko, and Takako, in the English language. Her account of the experience is entitled Windows for the Crown Prince (1952).

Prince Yoshi received his undergraduate degree in chemistry from the Faculty of Science at Gakushuin University in 1958. He subsequently did postgraduate work in the Faculty of Science at Tokyo University. In 1969, he became a Research Associate of the Japanese Foundation for Cancer Research specializing in the study of cellular division. The results of his research have been reported in the technical journals of the Japanese Cancer Association, as well as of the American Association for Cancer Research.

In 1997, Prince Hitachi received an honorary doctorate from George Washington University in the United States, and in April 2001 received another from the University of Minnesota. In March 1999, he became an honorary member of the German Association for Cancer Research, in recognition of his significant scientific contributions to the field of cancer research.

On 30 September 1964, the Prince married Hanako Tsugaru (born 19 July 1940), fourth daughter of the late Yoshitaka Tsugaru, a former count and a descendant of the daimyō of Tsugaru Domain. The following day, Emperor Shōwa granted him the title Hitachi-no-miya (Prince Hitachi), and authorization to start a new branch of the Imperial Family in celebration of his wedding.

Prince Hitachi and Princess Hitachi have their official residence in a palace in large gardens off Komazawadori in Higashi, Shibuya.^[1] They have no children.

Prince Hitachi is the honorary president of a wide variety of charitable organizations, especially those involving international exchange. Most recently, Prince and Princess Hitachi visited Nicaragua and El Salvador, to mark the 70th anniversary of the establishment of diplomatic relations with both countries in October 2005. They also made a visit to France in September 2007 and Peru, marking the celebration of 110 years since the establishment of a Japanese community in this country, June 2009.