A crimper, also known as a wire crimper, a crimping tool or a crimping pliers, is a tool used for crimping connectors onto wires. The most common types look similar to a pair of pliers or diagonal cutters, but other types exist, as do multi-function tools that combine crimping functions with those of a wire cutters and a wire stripper. A screw cutter may be included as well.  Crimpers for larger wires may consist of a die and anvil, where the work piece is sndwiched between the two, then the die is truck with a hammer to form the crimp.

Ratcheting crimpers will not release the work piece until a threshold pressure is delivered, ensuring that the work piece is not released until full compression is applied.  A safety mechanism may enable the ratchet to be released if the user determines that the tool is improperly applied to the work piece, or for some other reason decides not to complete the crimp.  Ratcheting crimpers may feature interchangeable dies, so that the same tool (frame) can be used to crimp a wide variety of connectors.

Most crimpers are not electrically insulated, having at most a cushion grip for comfort.  Crimpers with non-matching jaws may feature color-coded handles to help the user determine how to orient the tool to the workpiece.

Most often, crimping is used to make a strong electrical connection between a wire and a terminal, but crimping may be done for structural purposes as well.