The Real Instituto y Observatorio de la Armada (Royal Institute and Observatory of the Spanish Navy) is the scientific institute and astronomical observatory of the Spanish Navy (Armada), located in San Fernando in the Province of Cádiz, Andalusia, Spain.

[2] In 1790 the Royal Observatory in Madrid was built to take over the purely astronomical work of the facility at San Fernando.

In recent years the observatory has been adversely affected by light pollution.

[2] The observatory operated a time ball so that ships at sea could synchronize their clocks.

After better timekeeping at sea made it obsolete, it was disabled, but it was reactivated in the late 20th century every day at 13:00.