Princess Chichibu of Japan (9 September 1909 – 25 August 1995) was the wife of Prince Chichibu (Yasuhito) of Japan.
Princess Chichibu was born as Matsudaira Setsuko in Walton on Thames, England. She was the daughter of Matsudaira Tsuneo (1877–1949), Japanese ambassador to the United States (1924) and later to Great Britain (1928), and still later, Imperial Household Minister (1936–45, 1946–47) and his wife, the former Nabeshima Nobuko.
Although technically born a commoner, she was a scion of distinguished aristocratic families with close ties to the Japanese Imperial Family on both sides. Her paternal grandfather, Matsudaira Katamori, was the last daimyo of Aizu, a cadet branch of the Tokugawa dynasty. Her maternal grandfather was Marquis Nabeshima Naohiro, former daimyo of Saga. Her mother's elder sister, Itsuko (1882–1976), married Prince Nashimoto (Morimasa), an uncle of Empress Nagako.
In 1925, while her father was ambassador to the United States, Setsuko was educated at the Sidwell Friends School in Washington, D.C. (1925–1928). Upon her return to Japan, Empress Sadako chose Setsuko to marry her second son, Prince Chichibu. She married the Prince after her uncle, Viscount Matsudaira Morio, formally adopted her, thus removing the status incongruity between the prince and his bride, by making Setsuko the adopted daughter of a viscount.
On 28 September 1928, aged 19, she wed Prince Chichibu, and she became Princess Chichibu. Prince and Princess Chichibu had no children, as Princess Chichibu's only pregnancy ended in a miscarriage. But by all accounts their marriage was filled with love and happiness for each other.
In 1937, the prince and princess were sent on a tour of Europe which took several months. They represented Japan at the May 1937 coronation of Britain's King George VI and Queen Elizabeth in Westminster Abbey and subsequently visited Sweden and the Netherlands as the guests of King Gustav V and Queen Wilhelmina, respectively. Princess Chichibu stayed in Switzerland while her husband met Adolf Hitler in Nuremberg at the end of the trip. She felt a great love for the United States and for England and, as an anglophile, was greatly saddened by Japan's entry into the Second World War on the side of the Axis powers.
After the Prince's death of tuberculosis in 1953, Princess Chichibu became president of the Society for the Prevention of Tuberculosis, honorary president of the Britain-Japan Society, the Sweden-Japan Society, and an honorary vice president of the Japanese Red Cross. The Princess, who was fluent in English, made several semi-official visits to Great Britain and Sweden.
King Gustav VI Adolph of Sweden invested her with the Grand Cordon of the Order of the Seraphim on 8 April 1969. On 23 July 1962, she became an Dame Grand Cross of the Order of the British Empire. On 9 October 1978, Princess Margaret (on behalf of Queen Elizabeth II) invested Princess Chichibu as an Dame Grand Cross of the Order of St Michael and St George.
Princess Chichibu died of heart failure on 25 August 1995.
Her autobiography, which was published posthumously as The Silver Drum: A Japanese Imperial Memoir, was translated in English by Dorothy Britton.