A minelayer is any warship, submarine or military aircraft deploying explosive mines. Since World War I the term "minelayer" refers specifically to a naval ship used for deploying naval mines. "Mine planting" was the term for installing controlled mines at predetermined positions in connection with coastal fortifications or harbor approaches that would be detonated by shore control when a ship was fixed as being within the mine's effective range.

Before World War I, mine ships were termed mine planters generally. For example, in an address to the United States Navy ships of Mine Squadron One at Portland, England, Admiral Sims used the term “mine layer” while the introduction speaks of the men assembled from the “mine planters”. During and after that war the term "mine planter" became particularly associated with defensive coastal fortifications. The term "minelayer" was applied to vessels deploying both defensive- and offensive mine barrages and large scale sea mining. "Minelayer" lasted well past the last common use of "mine planter" in the late 1940s.

An army's special-purpose combat engineering vehicles used to lay landmines are sometimes called "minelayers".