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 Missouri, a trustee is responsible for managing a trust in accordance with the terms set forth by the grantor, who establishes the trust. The trustee can be the grantor themselves or another person or entity chosen by the grantor. Trust agreements often include provisions for successor trustees who will take over the trustee's responsibilities in the event of death, incapacity, resignation, or removal of the current trustee. Removal of a trustee can occur through a court order, which may be initiated by the trust's beneficiaries if they believe the trustee is not fulfilling their obligations. Trustees in Missouri are bound by a fiduciary duty to the trust's beneficiaries, which is the highest standard of care in legal and financial matters. This duty encompasses both a duty of care, meaning the trustee must prudently manage the trust as outlined in the trust agreement, and a duty of loyalty, which requires the trustee to act in the best interests of the beneficiaries and avoid conflicts of interest. Failure to adhere to these duties can lead to legal consequences, including potential removal by the court and financial liability for any harm caused to the trust's beneficiaries.