Biscotti are Italian almond biscuits originating in the city of Prato, Tuscany. They are twice-baked, oblong-shaped, dry, and crunchy. In Italy, they are known as cantucci, biscotti di Prato or biscotti etruschi and may be dipped in a drink, traditionally Vin Santo. Smaller biscotti may be known as biscottini or cantuccini. In Italian, the word biscotti (sg.: biscotto) encompasses all types of biscuits or cookies.

The Italian word biscotti (sg.: biscotto) originates from the Medieval Latin word biscoctus, meaning 'twice-cooked', which described items that were made from dough and baked twice, so they became very dry and could be stored for long periods of time. Such non-perishable food was particularly useful during journeys and wars, and twice-baked breads were a staple food of the Roman legions.

Biscotti, in this sense, shares its origin with the English biscuit (from Old French biscuit), which is used for a wide variety of baked goods, biscuits, crackers, and breads, only a few of which are actually baked twice.

In modern Italian, the word biscotto refers to any biscuit or cookie. The biscuit known to English-speakers as biscotti is usually called cantuccio, a word that means 'corner' but in the past meant the crust or heel of a loaf of bread. The words biscottini and cantuccini are diminutives that refer to smaller versions of biscotti or cantucci.

Although commonly used to indicate the biscuits of Prato, biscotti di Prato, in modern Italy they are also known widely by the name cantuccini. These names actually suggest other similar regional products of Italy. The term cantuccini is most commonly used today in Tuscany, but originally referred to variations or imitations which deviated from the traditional recipe in a few key points such as the use of yeasts, acids (to make them less dry), and flavourings. Rusks are larger, longer biscuits using rustic bread dough enriched with olive oil and anise seeds.

The confusion on the name may have been borne from the fact that on the old sign (still present) of "Biscottificio Antonio Mattei", the leading manufacturer of biscuits of Prato, written just below the name of the shop is "Manufacturers of cantuccini", which at the time was one of the major producers of the biscuits. The sign has remained unchanged, and after such a long time people are accustomed to associate the name cantuccini with the biscuits typical of Sardinia and Sicily.

In Spain and France, the Catalan carquinyoli (Catalan: [kəɾkiˈɲɔli]) or carquinyol is made with whole or sliced almonds. It is associated with inland Catalonia, Batea, La Fatarella, Prat de Comte, and in the Terra Alta.

Biscotti are traditional also in some inland towns in Valencia, where they are called rosegons or rosegós. In Menorca, carquinyols are square shaped and do not include whole almonds. One Catalan food writer states that the word carquinyoli is derived from the French croquignole, a French word of Germanic origin, but In France, a similar biscuit is known as croquant.