The Viện cơ mật or "Secret Institute" (chữ Nôm: 院機密; chữ Hán: 機密院; French: Conseil privé, Conseil d’État, Chambre haute),[1] established in 1834, was the Privy Council and key mandarin agency of the imperial court of Vietnam's final Nguyễn dynasty at Huế, until the end of the dynasty in 1945.

The Minh Mạng Emperor established the Viện cơ mật (Privy Council) along with the Nội các Viên (Cabinet, Grand Secretariat) as the main agencies of the court's administration.

[5] In the year 1834, Minh Mạng's political project (dự án chính trị) was expanded to Cambodia, the Siamese army attacked from the Vietnam-Laos border down to Hà Tiên province.

[5] In 1897 the Resident-Superior of Annam was granted the power to appoint the Nguyễn dynasty Emperors and presided over the meetings of the Viện cơ mật.

[8] During the reign of the Đồng Khánh Emperor a new great seal was made with the inscription Cơ mật chi ấn (機密之印) and a kiềm ấn (small seal) with the inscription Cơ mật (機密) that was 3 cm x 3 cm.