Matsuzo Nagai

was a Japanese diplomat and Olympic Games activist.

Biography He was born on 5 March 1877 in Aichi Prefecture.

He served in the Japanese delegation to the League of Nations in 1920, and served as Japanese Ambassador to Sweden and Finland in 1925–1930. In 1930, he formed part of the Japanese delegation to the London Naval Conference. He served as Ambassador to Germany from April 1933 to October 1934. After this, since at least mid-1935, he was the Japanese Ambassador to Latvia.

In 1936, he served as Minister of Transportation, and was an active supporter of naval expansion plans. In 1937, he was active in the Japanese governmental committee which was charged with preparing the Olympic games scheduled to take place in Tokyo in 1940, which was eventually cancelled. He also served as a member of the International Olympic Committee in 1939–1950.

He received the Grand Cross of the Royal Swedish Order of the Polar Star in 1928 and the Latvian Order of the Three Stars 1st Class on 5 July 1935. He died on 19 April 1957.