Étienne Bazeries (21 August 1846, in Port Vendres – 7 November 1931, in Noyon) was a French military cryptanalyst active between 1890 and the First World War.

In an effort to prompt reform within the government and enhance national security, Bazeries further exposed weaknesses in French cipher systems.

[1] In 1891, news of his talent had spread, and he began work for the Ministry of Foreign Affairs' Bureau du Chiffre.

Bazeries continued his cryptanalytic work there even after he retired from the Army in 1899, assisting in solving German military ciphers during World War I.

However, many of Bazeries recommendations to the government for improvements in official cipher systems met severe bureaucracy and rebuffs, which became a constant source of frustration for him in an otherwise illustrious career.