State archives of the canton of Valais, Cantonal archive in Sion, Switzerland.

The State Archives of the Canton of Valais (AEV) hold the canton's administrative and historical records, with holdings reaching back to 1005. Since May 2016 the administrative offices and consultation room have occupied the Arsenaux cultural centre in Sion, while the stacks lie entirely underground beneath the same building. Built in concrete with mobile shelving, they hold over 32 linear kilometres of archives and were designed by conservator Andrea Giovannini and building physicist Michel Bonvin with cantonal archivist Alain Dubois; work began in February 2017 and the last transfers took place in early 2020.

The archives grew out of the late 15th-century power struggle in which the Dizains challenged the prince-bishop and took over political affairs, keeping documents that protected the country's rights. In 1535 the Diet ordered the records stored in the fortified church of Valère, then had a dedicated building erected in Sion. During the great fire of 1788 the deputies evacuated the archives to Sierre, where most stayed until French troops arrived in 1798.

The archives' holdings reach back to a document of 1005, and the institution has published the yearbook Vallesia since 1946; its founder, André Donnet, was a medievalist who also wrote on revolutionary and 19th-century Valais. Since 1990 the archive has issued the Beihefte zu Vallesia series, reserved for dissertations, monographs and text editions too long for the yearbook; 29 volumes had appeared by 2015.

The reading room and administrative offices moved in May 2016 to the Arsenaux cultural centre in Sion; the storage vaults were built beneath that building between 2017 and 2020. The underground magazines, designed by Andrea Giovannini and Michel Bonvin with cantonal archivist Alain Dubois, hold over 32 linear kilometres of documents. Microfilm security copies are kept in a civil-defence shelter at 1,500 metres altitude.

The oldest document in the holdings dates from 1005, and the stacks built under the Arsenaux from 2017 can hold over 32 linear kilometres of archives. The underground magazines, designed by conservator Andrea Giovannini and building physicist Michel Bonvin, keep the records stable without human intervention.