Toothpaste is a paste or gel dentifrice that is used with a toothbrush to clean and maintain the aesthetics of teeth. Toothpaste is used to promote oral hygiene: it is an abrasive that aids in removing dental plaque and food from the teeth, assists in suppressing halitosis, and delivers active ingredients (most commonly fluoride) to help prevent tooth decay (dental caries) and gum disease (gingivitis). Due to variations in composition and fluoride content, not all toothpastes are equally effective in maintaining oral health. The decline of tooth decay during the 20th century has been attributed to the introduction and regular use of fluoride-containing toothpastes worldwide. Large amounts of swallowed toothpaste can be poisonous. Common colors for toothpaste include white (sometimes with colored stripes or green tint) and blue.

Since 5000 BCE, the Egyptians made a tooth powder, which consisted of powdered ashes of ox hooves, pumice, powdered and burnt eggshells and myrrh. The Greeks, and then the Romans, improved the recipes by adding abrasives such as crushed bones and oyster shells.

In the 9th century, the Iraqi musician and designer Ziryab invented a type of toothpaste which he popularized throughout Islamic Spain. The exact ingredients of this toothpaste are unknown, but it was reported to have been both "functional and pleasant to taste". It is not known whether these early toothpastes were used alone, were to be rubbed onto the teeth with rags, or were to be used with early toothbrushes, such as neem-tree twigs and miswak. During Japan's Edo period, inventor Hiraga Gennai's Hika rakuyo (1769) contained advertisements for Sosekiko, a "toothpaste in a box." Toothpastes or powders came into general use in the 19th century.

Tooth powders for use with toothbrushes came into general use in the 19th century in Britain. Most were homemade, with chalk, pulverized brick, or salt as ingredients. An 1866 Home Encyclopedia recommended pulverized charcoal, and cautioned that many patented tooth powders that were commercially marketed did more harm than good.

Arm & Hammer marketed a baking soda-based toothpowder in the United States until approximately 2000, and Colgate markets toothpowder in India and other countries.

An 18th-century American and British toothpaste recipe called for burned bread. Another formula around this time called for dragon's blood (a resin), cinnamon, and burned alum.^{[citation needed]}

In 1873 the Colgate company began the mass production of aromatic toothpaste in jars.

By 1900, a paste made of hydrogen peroxide and baking soda was recommended for use with toothbrushes. Pre-mixed toothpastes were first marketed in the 19th century, but did not surpass the popularity of tooth-powder until World War I.