The Reizei family (冷泉) is a branch of the clan Fujiwara.
For eight centuries, the family secretly preserved, under imperial order, an important collection of documents. On April 4, 1980, this collection of about 200,000 pieces was made public by Tametō Reizei (1914-1986). The following year, a library in Tokyo was created specially for their conservation. Not all of the documents have yet been identified, but certain ones have already been classified as national treasures.