* Early Seasons: Aaron Hotchner was the Unit Chief for the majority of the show's run. He was known for his strong leadership, analytical skills, and dedication to the team.
* Later Seasons: After Hotchner's departure, Matt Crawford took over as Unit Chief, but his tenure was short-lived.
* Final Season: Emily Prentiss ultimately became the Unit Chief, leading the team through its final season.
It's important to note that the leadership of the BAU was fluid throughout the show's run. Different characters took on leadership roles at various points, and some characters, like Rossi, had a strong influence on the team without technically holding the Unit Chief position.