A toothbrush is a special type of brush used to clean the teeth, gums, and tongue. It consists of a head of tightly clustered bristles, onto which toothpaste is applied, mounted on a handle that facilitates cleaning hard-to-reach areas of the mouth. They should be used in conjunction with tools that clean between the teeth―where toothbrush bristles cannot reach―such as floss, tape, interdental brushes or toothpicks.

Toothbrushes are available in different bristle textures, sizes, and forms. Most dentists recommend using soft-bristled toothbrushes, as harder ones may damage tooth enamel or irritate the gums.

Since many common toothpaste ingredients are harmful if swallowed in large amounts, toothpaste should be spat out. Brushing teeth is most often done at a sink in a bathroom or kitchen, where the toothbrush is rinsed afterwards to remove any debris remaining and then dried to reduce conditions ideal for bacterial growth (and, if it is a wooden toothbrush, mold as well).

Some toothbrushes have plant-based handles, often made of bamboo. However, most are made of cheap plastic; such brushes constitute a significant source of pollution. Over 1 billion toothbrushes are discarded into landfills annually in the United States alone. Bristles are commonly made of nylon (which, while not biodegradable like plastic, may still be recycled), bamboo viscose, or boar bristles.

Before the invention of the toothbrush, a variety of oral hygiene measures were used. This has been verified by excavations during which tree twigs, bird feathers, animal bones and porcupine quills were recovered.

The predecessor of the toothbrush is the chew stick. Chew sticks were twigs with frayed ends used to brush the teeth while the other end was used as a toothpick. The earliest chew sticks were discovered in Sumer in southern Mesopotamia in 3500 BC, an Egyptian tomb dating from 3000 BC, and mentioned in Chinese records dating from 1600 BC.

The Indian way of using tooth wood for brushing was presented by the Chinese monk Yijing (635–713 CE) in his description of the rules for monks: "Every day in the morning, a monk must chew a piece of tooth wood to brush his teeth and scrape his tongue, and this must be done in the proper way. Only after one has washed one's hands and mouth may one make salutations. Otherwise both the saluter and the saluted are at fault. In Sanskrit, the tooth wood is known as the dantakastha—danta meaning tooth, and kastha, a piece of wood. It is twelve finger-widths in length. The shortest is not less than eight finger-widths long, resembling the little finger in size. Chew one end of the wood well for a long while and then brush the teeth with it."

The Greeks and Romans used toothpicks to clean their teeth, and toothpick-like twigs have been excavated in Qin dynasty tombs. Chew sticks remain common in Africa and the rural Southern United States. In the Islamic world, the use of the chewing stick, or miswak, is regarded as a pious action and is prescribed for use before every prayer, occurring five times a day. Miswaks have been used by Muslims since the 7th century. Twigs of the neem tree were used by ancient Indians, and continue to be used today in India, although not hugely common, under the name datun. Neem, in its full bloom, can aid in healing by keeping the tooth and gum area clean and disinfected.