Domino is a type of game in which players score points by laying tiles (also called dominoes) edge to edge, such that each tile matches either an adjacent one or some specified total. The first player to reach a set number of points wins the game. Games can be played between two people or against a machine.

Dominoes are typically rectangular and twice as long as they are wide. They have a line down the middle to visually divide them into two squares, each of which is marked with an arrangement of spots, or pips, that are identical to those on a die. Most modern sets of dominoes are made from polymer materials such as ABS or PVC, although historically they have been made from a variety of natural materials: bone, silver lip ocean pearl oyster shell (mother of pearl), ivory, and dark hardwoods such as ebony. Many modern sets of dominoes are also manufactured from pressed cardboard.

In addition to the traditional blocking and scoring games, there are a number of other domino variants which focus on skill or chance. These include solitaire dominoes, which are adaptations of card games that were once popular in certain areas to circumvent religious proscriptions against playing cards; and trick-taking games, in which players compete to win a hand by taking the highest number of tricks. A variety of other domino games can be played with a single-six set; these vary in difficulty and are sometimes used to practice skills in preparation for more complex games.

The earliest known use of the term domino occurred in the 18th century, when it was used to describe a sequence of events that led to an actual chain reaction. The word later came to be used metaphorically, often in reference to the impact of a single event on subsequent events. This use of the term is also known as domino effect.

A person who builds an impressive arrangement of dominoes is referred to as a domino artist or, more commonly, simply as a domino builder. The most elaborate domino setups are created by professional artists who create shows before live audiences. These shows can involve hundreds or even thousands of dominoes set up in careful sequence, and all toppled with the nudge of only one.

For a domino artist to be successful, it is important for her to understand how the pieces will fit together and how to anticipate that a single accidental topple can bring the whole display crashing down. For this reason, most domino artists practice fractions when preparing their installations. For example, Lily Hevesh uses fractions to determine how many dominoes she will need to create a 24-inch-long line and how they will be arranged. This allows her to avoid the small accidental topples that are bound to occur in any project.