Which title refers to the highest enlisted rank within a platoon?

The title that refers to the highest enlisted rank within a platoon is First Sergeant. This rank typically serves as the primary leader and advisor for a unit's soldiers, holding responsibility for their training, discipline, and welfare. The First Sergeant is often regarded as the backbone of the unit, providing command and control and facilitating communication between the enlisted soldiers and the officers.

In contrast, while a Sergeant First Class is an important leadership position, it generally ranks just below the First Sergeant within the enlisted hierarchy. The roles of Captain and Major pertain to officer ranks, with a Captain typically commanding a company, which consists of multiple platoons, and a Major serving as a tactical officer or staff officer in a larger command. Hence, within the context of a platoon, the First Sergeant clearly holds the highest enlisted rank.