The Declaration of London is an international code of maritime law, especially as it relates to wartime activites, proposed in 1909 by the leading European naval powers, as well as the United States and Japan, after a multinational conference that occurred in 1908 in London.

Although it dealt with many controversial points, including blockades, contraband and prize, it largely reiterated existing law, although it showed greater regard to the rights of neutral entities.

The declaration was ratified by the United States Senate, but not by many other powers; it never went into effect officially.