An informal role for whoever drives BIM adoption and best practice inside a firm - distinct from BIM Manager or BIM Coordinator, which are formal project or organizational roles. A BIM Champion doesn't necessarily hold a job title with "BIM" in it - often it's simply the most enthusiastic, capable person on a team who ends up training colleagues, pushing for better standards, and advocating for tools and workflows, long before the firm formalizes that role into an actual BIM Manager position.