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 Colorado, a trustee is responsible for managing a trust in accordance with the terms set forth by the grantor and in the best interests of the beneficiaries. The trustee's role includes a fiduciary duty, which is a legal obligation to act in the best interest of the trust's beneficiaries. This duty encompasses both a duty of care, ensuring that the trustee administers the trust competently and prudently, and a duty of loyalty, requiring the trustee to avoid conflicts of interest and to not use the trust property for personal gain. Successor trustees can be appointed in the trust agreement to take over if the original trustee can no longer serve due to death, incapacity, resignation, or removal by the court. In Colorado, the administration of trusts is governed by the Colorado Trust Code, which outlines the responsibilities, powers, and duties of trustees, as well as the rights of beneficiaries.