In trust law, a spendthrift trust is a trust that is created for the benefit of a person (often unable to control his/her spending) that gives an independent trustee full authority to make decisions as to how the trust funds may be spent for the benefit of the beneficiary. Creditors of the beneficiary generally cannot reach the funds in the trust, and the funds are not actually under the control of the beneficiary.

The creator of a trust is often called the "trustor", "grantor", or "settlor" of the trust. A trust generally will not be treated as a spendthrift trust unless the trust agreement contains language showing that the creator intended the trust to qualify as spendthrift. This is what is known as a spendthrift clause or spendthrift provision.

A spendthrift provision creates an irrevocable trust preventing creditors from attaching the interest of the beneficiary in the trust before that interest (cash or property) is actually distributed to him or her. Most well-drafted irrevocable trusts contain spendthrift provisions even though the beneficiaries are not known to be spendthrifts. This is because such a provision protects the trust and the beneficiary in the event a beneficiary is sued and a judgment creditor attempts to attach the beneficiary's interest in the trust.

The protection of the spendthrift trust extends solely to the property that is in the trust. Once the property has been distributed to the beneficiary that property can be reached by a creditor, except to the extent the distributed property is used to support the beneficiary. If a trust calls for a distribution to the beneficiary, but the beneficiary refuses such distribution and elects to retain property in the trust, the spendthrift protection of the trust ceases with respect to that distribution and the beneficiary's creditors can now reach trust assets.^{[citation needed]}

Some creditors may compel payment out of the trust, particularly those who supply the beneficiary with "necessaries" (usually food and shelter, but sometimes clothing and transportation, if these are not extravagant). Most jurisdictions also permit the invasion of spendthrift trust assets to satisfy awards of child support and alimony.

A trust created by an individual for his or her own benefit is sometimes called a "self-settled trust", and may be a kind of asset-protection trust. If the creator of a self-settled trust is also a beneficiary of the trust, particular problems arise regarding the protection of assets from creditors, and the prevention of fraud, that is, the possibility that the creator of the trust seeks to defraud creditors.

To prevent individuals from creating trusts to defeat their own creditors, the laws of most states provide that a spendthrift clause in a trust document does not protect the beneficiary to the extent that the beneficiary is also the person who created the trust. The settlor does not need to be either the sole settlor or the only beneficiary of the trust. As long as the settlor is a beneficiary of the trust to any extent, to that extent the trust will be deemed self-settled.^{[citation needed]} For example, Texas law provides:

Further, laws in some states (like Texas) are worded so broadly that anyone transferring property to the trust might be deemed to be a "creator" (i.e., settlor, grantor, or trustor), not merely the person or persons who originally set up the trust.