Employee stock options (ESO) is a label that refers to compensation contracts between an employer and an employee that carries some characteristics of financial options.

Employee stock options are commonly viewed as an internal agreement providing the possibility to participate in the share capital of a company, granted by the company to an employee as part of the employee's remuneration package. Regulators and economists have since specified that ESOs are compensation contracts.

These nonstandard contracts exist between employee and employer, whereby the employer has the liability of delivering a certain number of shares of the employer stock, when and if the employee stock options are exercised by the employee. The contract length varies, and often carries terms that may change depending on the employer and the current employment status of the employee. In the United States, the terms are detailed within an employer's "Stock Option Agreement for Incentive Equity Plan". Essentially, this is an agreement which grants the employee eligibility to purchase a limited amount of stock at a predetermined price. The resulting shares that are granted are typically restricted stock. There is no obligation for the employee to exercise the option, in which case the option will lapse.

AICPA's Financial Reporting Alert describes these contracts as amounting to a "short" position in the employer's equity, unless the contract is tied to some other attribute of the employer's balance sheet. To the extent the employer's position can be modeled as a type of option, it is most often modeled as a "short position in a call". From the employee's point of view, the compensation contract provides a conditional right to buy the equity of the employer and when modeled as an option, the employee's perspective is that of a "long position in a call option".