A crimper,[1]​[2][3]​ also known as crimping pliers,[4]​ terminal pliers, staple pliers, compression pliers, crimping pliers[5]​ crimping pliers,[6]​ or crimping pliers[6]​ or crimping pliers is a tool used to corrugate[7]​ or crimp[1]​ two pieces of metal or other malleable materials by deforming one or both pieces; This deformation is what keeps them together.

This technique is usually used to join terminals with insulating coating, connectors (F, BNC, RJ9, RJ11, RJ12, RJ45[6]​[8]​) and telecommunications cables (coaxial, and twisted pair). There are also them for fiber optics.

The crimping tool is most widely used in metalworking. It is frequently used to secure bullets in their cartridges, for quick but durable electrical connections, to secure lids on food cans and many other applications. Because it can be used in cold working techniques, the crimping tool can also be used to form a strong bond between the workpiece and a non-metallic component.

When joining segments of tubular sheet metal pipe, such as flue pipes for wood stoves, downspouts for rain gutters, or for installing ventilation ducts, one end of a pipe is treated with a crimping tool to make a slip joint on the next section of duct. Thus, the gasket will not retain liquids, but will be suitable for transporting low-pressure fluids. Crimp joints can be arranged to prevent dirt buildup.