The BL 7.5-inch howitzer (naval) was a British anti-submarine mortar developed during World War I.

The weapon was developed together with other similar devices early in 1917 and went into service in June 1917 in response to German unrestricted submarine warfare.

However the small weight of the shell limited its effectiveness,[3] and the anti-submarine mortar did not become a truly successful weapon until the advent of the multiple-projectile Hedgehog during World War II.

Nonetheless Admiral John Jellicoe, writing a few years after the gun had gone into service, commented: "This weapon, although not very popular at first, soon, however, proved its value, when employed both from patrol craft and from merchant ships.

"[3] Two were mounted on HMS Vindictive and used to bombard German defences during her participation in the Zeebrugge raid of 23 April 1918.