The Lioré et Olivier LeO 25 was a bomber aircraft produced in France in the late 1920s. It was a development of the LeO 20 and retained much of that aircraft's structure, adding a new tail and liquid-cooled engines. The prototype was delivered to the Aéronautique Militaire amongst a batch of LeO 20s in 1928 for evaluation. This was redesignated LeO 252 in 1929 after an engine change, and a second, generally similar machine was purchased by Romania.
In 1931, the LeO 252 remaining in France was fitted with wooden floats and handed over to the Aéronavale, forming the pattern for the majority of LeO 25s which would be produced as seaplanes. The only other members of the family to be built with wheeled undercarriage were three LeO 253s purchased by Brazil in 1931, and which would see service in the Constitutionalist Revolution the following year, and the sole LeO 255 which would later be fitted with floats. This latter machine was equipped with supercharged engines and was used to set a number of height-with-load records for seaplanes.
The only versions produced in quantity were the LeO H-257bis and LeO H-258, which together represented orders for 86 units from the Aéronavale. Entering service in June 1935, they flew neutrality patrols during the Spanish Civil War and some remained in service at the outbreak of the Second World War. These surviving aircraft flew convoy escort and anti-submarine patrols in September 1939 before being used as tactical bombers against land targets during the Blitzkrieg, suffering heavy losses. Fifty-three remained on strength with Vichy forces in August 1940, and these were used for secondary roles such as training and target towing until 1944.