Yamaguchi Prefectural Archives (山口県文書館, Yamaguchi-ken Monjo-kan) opened in Yamaguchi, Yamaguchi Prefecture, Japan, in 1959 as the country's first dedicated modern archival institution.

[2][3][4] In Shōwa 27 (1952), the Mōri family, former daimyō of Chōshū Domain, deposited its domainal documents with Yamaguchi Prefecture, whereupon they were stored, alongside materials gathered by the pre-war Prefectural History Compilation Office, at Yamaguchi Prefectural Library (ja).

[5] These items were transferred in with the opening of Yamaguchi Prefectural Archives in 1959; donations and deposits - including materials from the Tokuyama Domain Mōri family - have continued since.

[5] The archives holds approximately 530,000 documents, roughly divided into five groups:[1] The holdings include seven Important Cultural Properties, two Prefectural Cultural Properties, and three Municipal Tangible Cultural Properties.

[6]