A microtome (from the Greek mikros, meaning "small", and temnein, meaning "to cut") is a cutting tool used to produce extremely thin slices of material known as sections, with the process being termed microsectioning. Important in science, microtomes are used in microscopy for the preparation of samples for observation under transmitted light or electron radiation.

Microtomes use steel, glass or diamond blades depending upon the specimen being sliced and the desired thickness of the sections being cut. Steel blades are used to prepare histological sections of animal or plant tissues for light microscopy. Glass knives are used to slice sections for light microscopy and to slice very thin sections for electron microscopy. Industrial grade diamond knives are used to slice hard materials such as bone, teeth and tough plant matter for both light microscopy and for electron microscopy. Gem-quality diamond knives are also used for slicing thin sections for electron microscopy.

Microtomy is a method for the preparation of thin sections for materials such as bones, minerals and teeth, and an alternative to electropolishing and ion milling. Microtome sections can be made thin enough to section a human hair across its breadth, with section thickness between 50 nm and 100 μm.