Embezzlement is the act of dishonestly appropriating or secreting assets, usually financial in nature, by one or more individuals to whom such assets have been entrusted. For instance, a clerk or cashier handling large sums of money can embezzle cash from his or her employer, a lawyer can embezzle funds from clients' trust accounts, a financial advisor can embezzle funds from investors, or a spouse can embezzle funds from his or her partner. Embezzlement may range from the very minor in nature, involving only small amounts, to the immense, involving large sums and sophisticated schemes. More often than not, embezzlement is performed in a manner that is premeditated, systematic and/or methodical, with the explicit intent to conceal the activities from other individuals, usually because it is being done without their knowledge or consent. Often it involves the trusted person embezzling only a small proportion or fraction of the funds received, in an attempt to minimize the risk of detection. If successful, embezzlements can continue for years (or even decades) without detection. It is often only when the funds are needed, or called upon for use, that the victims realize the funds or savings are missing and that they have been duped by the embezzler.

Embezzlement differs from larceny in two ways. First, in embezzlement, an actual conversion must occur; second, the original taking must not be trespassory. To say that the taking was not trespassory is to say that the person(s) performing the embezzlement had the right to possess, use, and/or access the assets in question, and that such person(s) subsequently secreted and converted the assets for an unintended and/or unsanctioned use. Conversion requires that the secretion interferes with the property, rather than just relocate it. As in larceny, the measure is not the gain to the embezzler, but the loss to the asset stakeholders. An example of conversion is when a person logs checks in a check register or transaction log as being used for one specific purpose and then explicitly uses the funds from the checking account for another and completely different purpose.

Historically, embezzlement was created by statute to deal with situations where secretion could occur while the perpetrator him or herself was innocent of larceny typically because of the "lawful possession" element. That is, embezzlement fills in the blanks where larceny laws do not apply. The first general embezzlement statute was enacted in England in 1799. The statute was passed in reaction to the decision of King v. Bazeley, 2 Leach 835, 168 Eng. Rep. 517 (Cr. Cas. Res. 1799). In Bazeley, a customer of a bank had given a teller a note to be deposited to the customer's account. The teller immediately pocketed the note. The appropriation was soon discovered and the teller was charged with larceny. The issue before the court was whether the actions of the teller constituted larceny. The court held that that the actions did not constitute larceny because the teller had lawful possession of the note at the time of the conversion. Bazeley's demonstrates the unreasonable limitations in the scope of common law larceny. In Bazeley, had the clerk placed the note in the till before deciding to steal it then the crime would have been larceny since by placing the note in the till the bank acquired constructive possession of the note and the subsequent appropriation of the note by the teller would constitute a trespassory taking.