Who on your project will have the authority to make decisions at the most senior level? Who will get you access to the resources you require? Who will unblock problems and sign off the extra money the project needs?
These are all functions of a Project Board (or Steering Group).

Michel Dion, PMP, CPA
Founder and Developer of Project-Aria
Discover my book:
Leadership Toolbox for Project Managers: Achieve Better Results in a Dynamic World