Minelaying is the act of deploying explosive mines. Historically this has been carried out by ships, submarines and aircraft. Additionally, the term Minelayer refers specifically to a naval ship used for deploying sea mines. The term also sometimes refers to an army's special-purpose combat engineering vehicles used to lay land mines.
The most common use of the term "minelayer" is a naval ship used for deploying sea mines. Probably the most famous minelayer in history is the Ottoman Empire's Navy's Nusrat, active during the Gallipoli Campaign of the First World War. Nusrat laid the mines that sank , , and the French battleship Bouvet in the Dardanelles on 18 March 1915. The Russian minelayer Amur was also efficient; it sunk the Japanese battleships Hatsuse and Yashima in 1904 during the Russo-Japanese War.
In World War II, the British employed the Abdiel class minelayers both as minelayers and as transports to isolated garrisons, such as Malta and Tobruk. Their combination of high speed (up to 40 knots) and carrying capacity was highly valued. The French used the same concept for the Pluton.
A naval minelayer can vary considerably in size, from coastal boats of several hundred tonnes in displacement to destroyer-like ships of several thousand tonnes in displacement. Apart from their loads of sea mines, most would also carry other weapons for self-defense.
In modern times, most navies worldwide no longer possess any minelaying vessels; the United States Navy, for example, uses aircraft to lay sea mines instead. A few navies still have minelayers in commission; these include South Korea, Norway, Sweden and Finland, countries with long, shallow coastlines where sea mines are most effective.