An ERISA Plan Sponsor is most often the employer who sponsors the benefit plan at issue. Thus, for example, the ABC Company is the plan sponsor of the ABC Company medical plan. With multiemployer benefit plans for union employees, the sponsor is generally the Board of Trustees of the multiemployer plan. A plan sponsor is not a fiduciary. An ERISA Plan Administrator is a fiduciary charged with administering the plan. By default, the Plan Sponsor is also the Plan Administrator, but the sponsor can designate someone or something (like a committee) else to serve as the Plan Administrator.