The Key 3 in the Order of the Arrow (OA) is a group of three leaders that meet regularly to establish goals and evaluate progress: 

Lodge chief: Chairs the Lodge Executive Committee and presides over meetings

Lodge adviser: A volunteer adult who advises the lodge

Staff adviser: A professional who advises the lodge

The Key 3's role is to ensure that lodge officers and committees can successfully carry out the lodge's operations. They meet regularly at each level of the OA, including the chapter, lodge, section, region, and national levels.