A trustee is a person or entity designated by a person who creates a trust (grantor, settlor, or trustor) to manage and administer the trust for the benefit of the named beneficiary or beneficiaries. The trustee of a trust created for estate planning purposes is often the grantor, settlor, or trustor who created and funded the trust.

A trust agreement may designate one or more successor trustees who will become the trustee if the previous trustee dies, is unable to continue to serve as trustee, resigns as trustee, or is removed by court order following a lawsuit filed by the beneficiary or beneficiaries of the trust.

A trustee has a fiduciary duty to the beneficiary or beneficiaries of the trust. A fiduciary duty includes the highest duty of care (performance of duties under the terms of the trust agreement) and of loyalty (avoiding conflicts of interest) recognized in law.

In California, a trustee is responsible for managing a trust in accordance with the terms set forth by the grantor, who may also serve as the initial trustee. The trust document typically outlines the procedures for appointing successor trustees in the event the original trustee can no longer fulfill their duties due to death, incapacity, resignation, or removal. Successor trustees step in to ensure continuity in the management of the trust. Trustees in California are bound by a fiduciary duty, which is a legal obligation to act in the best interest of the beneficiaries. This duty encompasses both a duty of care, meaning the trustee must manage the trust assets prudently and in accordance with the trust's terms, and a duty of loyalty, which requires the trustee to avoid conflicts of interest and to administer the trust solely for the benefit of the beneficiaries. Failure to adhere to these duties can lead to legal action by the beneficiaries, and the trustee can be held liable for breaches of fiduciary duty.