Chokusen Wakashu (勅撰和歌集)
The term "chokusen wakashu" represents an anthology of Japanese poetry complied under order of an emperor or a retired emperor. Starting with the Kokin Wakashu (Collection of Ancient and Modern Japanese Poetry) (completed in 905) until the Shinshoku Kokin Wakashu (New Continued Collection of Ancient and Modern Japanese Poetry) (completed in 1439), 21 chokusen wakashu were compiled during the 534 years. These 21 anthologies are commonly known together as 'Nijuichidai-shu' (The Twenty-One Collections of Japanese Poetry). There is also a quasi-Imperial anthology called Shinyo Wakashu (Collection of New Pages), which was compiled by the Southern Court. Imperial anthologies are classified into three groups according to the year of compilation: Sandai-shu (Three Major Collections of Japanese Poetry) (containing the Collection of Ancient and Modern Japanese Poetry, the Later Collection of Japanese Poetry, and the Collection of Gleanings), Hachidai-shu (Eight Major Collections of Japanese Poetry) (see below), and Jusandai-shu (Thirteen Major Collections of Japanese Poetry) (see below).
(Note that the Sandai-shu anthologies are also included in the Hachidai-shu)