A surety is a person who agrees to be responsible for the debt or obligation of another. Additionally, the situation in which a surety is most typically required is when the ability of the primary obligor or principal to perform its obligations under a contract is in question, or when there is some public or private interest which requires protection from the consequences of the principal's default or delinquency. In most common law jurisdictions, a contract of suretyship is subject to the statute of frauds (or its equivalent local laws) and is only enforceable if recorded in writing and signed by the surety and the principal.

If the surety is required to pay or perform due to the principal's failure to do so, the law will usually give the surety a right of subrogation, allowing the surety to "step into the shoes of" the principal and use his contractual rights to recover the cost of making payment or performing on the principal's behalf, even in the absence of an express agreement to that effect between the surety and the principal.

The act of becoming a surety is also called a guarantee. Traditionally a guarantee was distinguished from a surety in that the surety's liability was joint and primary with the principal, whereas the guaranty's liability was ancillary and derivative, but many jurisdictions have abolished this distinction.

In the United States, under Article 3 of the Uniform Commercial Code, a person who signs a negotiable instrument as a surety is termed an accommodation party; such a party may be able to assert defenses to the enforcement of an instrument not available to the maker of the instrument.

See also

• Aval
• Co-signing
• Indemnity
• Surety bond
• Surety (Canadian criminal law)