The Japanese monarchy is the oldest continuous hereditary monarchy in the world. The imperial house recognizes 125 monarchs beginning with the legendary Emperor Jimmu (traditionally dated to February 11, 660 BC) and continuing up to the current emperor, Akihito; see its family tree.
Historical evidence for the first 25 emperors is marginal by modern standards, but there is firm evidence for the hereditary line since Emperor Keitai ascended the throne 1500 years ago.
Article 5 of the Imperial Household Law (皇室典範 Kōshitsu Tenpan?) defines the imperial family (皇族?) as the empress (皇后 kōgō?); the empress dowager (皇太后 kōtaigō?); the grand empress dowager (太皇太后 tai-kōtaigō?); Emperor's legitimate sons and legitimate grandsons in the legitimate male-line (親王 shinnō?) and their consorts (親王妃 shinnōhi?); Emperor's unmarried legitimate daughters and unmarried legitimate granddaughters in the legitimate male-line (内親王 naishinnō?); Emperor's other male descendants in the legitimate male-line (王 ō?) and their consorts (王妃 ōhi?); and the Emperor's other unmarried female descendants in the legitimate male-line (女王 joō?). In English, shinnō and ō are both translated as "prince" as well as shinnōhi, naishinnō, ōhi and joō as "princess".
After the removal of 11 collateral branches from the Imperial House in October 1947, the official membership of the imperial family has effectively been limited to the male line descendants of the Emperor Taishō, excluding females who married outside the imperial family and their descendants.
There are presently 21 members of the Imperial Family:
- The Emperor was born at Tokyo Imperial Palace on 23 December 1933, the elder son and sixth child of the Emperor Shōwa and Empress Kōjun. He was married on 10 April 1959 to Michiko Shōda. Emperor Akihito succeeded his father as emperor on 7 January 1989.
- The Empress, formerly Michiko Shōda, was born in Tokyo on 24 October 1934, the eldest daughter of Hidesaburo Shōda, president and honorary chairman of Nisshin Flour Milling Inc.
- The Crown Prince, the eldest son of the Emperor and the Empress, was born in the Hospital of the Imperial Household in Tokyo on 23 February 1960. He became heir apparent upon his father's accession to the throne. Crown Prince Naruhito was married on 10 June 1993 to Masako Owada.
- The Crown Princess was born on 9 December 1963, the daughter of Hisashi Owada, a former vice minister of foreign affairs and former permanent representative of Japan to the United Nations. The Crown Prince and Crown Princess have one daughter:
- The Princess Toshi (born 1 December 2001)
- The Prince Akishino, the Emperor's second son, was born on 11 November 1965. His childhood title was Prince Aya. He received the title Prince Akishino and permission to start a new branch of the imperial family upon his marriage to Kiko Kawashima on 29 June 1990.
- The Princess Akishino was born on 11 September 1966, the daughter of Tatsuhiko Kawashima, professor of economics at Gakushuin University. Prince and Princess Akishino have two daughters and a son:
- Princess Mako of Akishino (born 23 October 1991)
- Princess Kako of Akishino (born 29 December 1994)
- Prince Hisahito of Akishino (born 6 September 2006)
- The Prince Hitachi was born on 28 November 1935, the second son and seventh child of the Emperor Shōwa and Empress Kojun. His childhood title was Prince Yoshi. He received the title Prince Hitachi and permission to set up a new branch of the imperial family on 1 October 1961, the day after his wedding.
- The Princess Hitachi was born on 19 July 1940, the daughter of former Count Yoshitaka Tsugaru. Prince and Princess Hitachi have no children.
The Prince Mikasa was born on 2 December 1915, the fourth son of the Emperor Taishō and Empress Teimei. He is the surviving brother of Emperor Shōwa and the surviving paternal uncle of Emperor Akihito. His childhood title was Prince Sumi (Sumi-no-miya). He received the title Prince Mikasa and permission to start a new branch of the imperial family on 2 December 1935. He married on 22 October 1941. The Princess Mikasa was born on 6 June 1923, the second daughter of Viscount Masanori Takagi. Prince and Princess Mikasa have two daughters and three sons.
- 'Princess Tomohito of Mikasa' is the widow of Prince Tomohito of Mikasa (born 5 January 1946, died 6 June 2012), the eldest son of the Prince and Princess Mikasa and a first cousin of Emperor Akihito. The princess was born on 9 April 1955, the daughter of Takakichi Asō, chairman of Asō Cement Co. and his wife, Kazuko, a daughter of former prime minister Shigeru Yoshida. Has two daughters with the late Prince Tomohito of Mikasa:
- Princess Akiko of Mikasa (born 20 December 1981)
- Princess Yōko of Mikasa (born 25 October 1983)
- The Princess Takamado is the widow of The Prince Takamado (born 29 December 1954, died 21 November 2002), the third son of the Prince and the Princess Mikasa and a first cousin of Emperor Akihito. The princess was born 10 July 1953, the daughter of Shigejiro Tottori. She married the prince on 6 December 1981. Originally known as *Prince Norihito of Mikasa, he received the title Prince Takamado and permission to start a new branch of the imperial family on 1 December 1981. Princess Takamado has three daughters:
- Princess Tsuguko of Takamado (born 6 March 1986)
- Princess Noriko of Takamado (born 22 July 1988)
- Princess Ayako of Takamado (born 15 September 1990)