Mortar and pestle is a set of two simple tools used from the Stone Age to the present day to prepare ingredients or substances by crushing and grinding them into a fine paste or powder in the kitchen, laboratory, and pharmacy. The mortar () is characteristically a bowl, typically made of hard wood, metal, ceramic, or hard stone such as granite. The pestle (, also US: ) is a blunt, club-shaped object. The substance to be ground, which may be wet or dry, is placed in the mortar where the pestle is pounded, pressed, and rotated into the substance until the desired texture is achieved.

Mortars and pestles have been used in cooking since prehistory; today they are typically associated with the profession of pharmacy due to their historical use in preparing medicines. They are used in chemistry settings for pulverizing small amounts of chemicals; in arts and cosmetics for pulverizing pigments, binders, and other substances; in ceramics for making grog; in masonry and in other types of construction requiring pulverized materials. In cooking, they are typically used to crush spices, to make pesto and certain cocktails such as the mojito, which requires the gentle crushing of sugar, ice, and mint leaves in the glass with a pestle.

The invention of mortars and pestles seems related to that of quern-stones, which use a similar principle of naturally indented, durable, hard stone bases and mallets of stone or wood to process food and plant materials, clay, or minerals by stamping, crushing, pulverizing and grinding.

A key advantage of the mortar is that it presents a deeper bowl for confining the material to be ground without the waste and spillage that occurs with flat grinding stones. Another advantage is that the mortar can be made large enough for a person to stand upright and adjacent to it and use the combined strength of their upper body and the force of gravity for better stamping. Large mortars allow for several people with several pestles to stamp the material faster and more efficiently. Working over a large mortar that a person can stand next to is physically easier and more ergonomical (by ensuring a better posture of the whole body) than for a small quern, where a person has to crouch and use the uncomfortable, repetitive motion of hand grinding by sliding.

Mortars and pestles anticipate modern blenders and grinders and can be described as having the function of small, mobile, hand-operated mills that don't require electricity or fuel to operate.

Large wooden mortars and wooden pestles would predate and lead to the invention of butterchurns, as domestication of livestock and use of dairy (during the Neolithic) came well after the mortar and pestle. Butter would be churned from cream or milk in a wooden container with a long wooden stick, very like the use of wooden mortars and pestles.