A center of excellence(COE) is a team, a shared facility or an entity that provides leadership, best practices, research, support and/or training for a focus area. Due to its broad usage and vague legal precedent, a "center of excellence" in one context may have completely different characteristics from another.
Within an organization, a center of excellence may refer to a group of people, a department or a shared facility. It may also be known as a competency center or a capability center. Stephen Jenner and Craig Kilford, in Management of Portfolios, mention COE as a coordinating function which ensures that change initiatives are delivered consistently and well, through standard processes and competent staff.