The Canon de 138 mm Modèle 1910 was a medium calibre naval gun of the French Navy used during World War I and World War II. It was carried by the dreadnoughts of the Courbet and Bretagne classes as their secondary armament and planned for use in the Normandie-class battleships. It was used as the primary armament for the Arras-class sloops and planned for the light cruiser Lamotte Picquet that was canceled in 1915. It was also used in coast defense batteries during both World Wars.