A mousetrap is a specialized type of animal trap designed primarily to catch mice; however, it may also trap other small animals. Mousetraps are usually set in an indoor location where there is a suspected infestation of rodents. There are various types of mousetrap, each with its own advantages and disadvantages. Larger traps are designed to catch other species of animals; such as rats, squirrels, other small rodents, or other animals.

The first spring-loaded mouse trap was invented by William C. Hooker of Abingdon Illinois, who received US patent 528671 for his design in 1894.James Henry Atkinson, a British inventor who in 1897 invented a prototype called the "Little Nipper", probably had seen the Hooker trap in the shops or in advertisements and used it as the basis of his model.

It is a simple device with a heavily spring-loaded bar and a trip to release it. Cheese may be placed on the trip as bait, but other food such as oats, chocolate, bread, meat, butter and peanut butter are commonly used. The spring-loaded bar swings down rapidly and with great force when anything, usually a mouse, touches the trip. The design is such that the mouse's neck or spinal cord will be broken, or its ribs or skull crushed, by the force of the bar. The trap can be held over a toilet or bin and the dead mouse released into it by pulling the bar. Rats are much larger than mice; a much larger version of the same type of trap is used to kill them. Some spring mouse traps have a plastic extended trigger made to look like a piece of cheese. The larger trigger has two advantages over the smaller traditional type:1)increased leverage, which requires less force from the rodent to trip it and 2) the larger surface area of the trigger increases the probability of even the most cunning of rodents to set off the trap.