Coin collecting is the collecting of coins or other forms of minted legal tender. Coins of interest to collectors include beautiful, rare, and historically significant pieces. Collectors may be interested, for example, in complete sets of a particular design or denomination, coins that were in circulation for only a brief time, or coins with errors. Coin collecting can be differentiated from numismatics, in that the latter is the systematic study of currency as a whole, though the two disciplines are closely interlinked.

Mint-made errors occur when coins are made incorrectly at the mint, including anything that happens to the coin up until the completion of the minting process. Mint error coins can be the result of deterioration of the minting equipment, accidents or malfunctions during the minting process, or interventions by mint personnel. Coins are inspected during production and errors are typically caught. However, some are inadvertently released into circulation. Modern production methods eliminate many errors and automated counters are effective at removing error coins. Damage occurring later may sometime resemble true mint errors. Error coins may be of value to collectors depending on the rarity and condition. Some coin collectors specialize in error coins.