An irrevocable trust is a trust that cannot be amended, modified, or terminated by the grantor, settlor, or trustor (person who created the trust) after it is created—at least not without the permission of the beneficiary or beneficiaries.

Irrevocable trusts generally offer tax benefits that revocable trusts do not. This is primarily because the grantor, settlor, or trustor who creates an irrevocable trust permanently transfers (gifts) all right of ownership of the assets to the trust and its beneficiaries.

Laws vary from state to state but a trust is usually irrevocable unless the grantor, settlor, or trustor specifies otherwise in the trust agreement.

In California, an irrevocable trust is a type of trust that, once established, typically cannot be changed, modified, or terminated by the person who created it, known as the grantor, settlor, or trustor, without the consent of the beneficiaries. The main characteristic of an irrevocable trust is the transfer of ownership of the grantor's assets to the trust, effectively removing the assets from the grantor's taxable estate. This can result in significant tax advantages, such as reduced estate taxes and gift taxes, since the assets are no longer considered part of the grantor's property. California law presumes that a trust is revocable unless the trust document explicitly states it is irrevocable. The California Probate Code governs the creation and administration of irrevocable trusts, and any changes to such trusts must comply with the relevant statutory provisions and may require court approval or the consent of all beneficiaries.