ERISA defines the term Fiduciary to include any person who
Has discretionary authority or responsibility in the administration of a plan
Exercises any discretionary authority or control with respect to plan assets
Renders investment advice as to plan assets for a fee
For plans (such as Church plans) that are exempt from ERISA, state law contains similar concepts.
Examples of plan fiduciaries would be retirement plan committees, heads of school, business managers or any other individual and/or committee that exercises discretionary authority in the administration of the retirement plan.