Ensign first class is a rank of officer in naval services and space forces, most notably the Starfleet of the United Federation of Planets.

An ensign first class is one of the most basic officer ranks, a grade higher than an ensign and a grade below lieutenant junior grade in some rank structures. This grade of ensign rank is roughly equivalent with the authority of a lieutenant of military forces, but many services have no direct analog, with this grade falling between second lieutenant and first lieutenant without an equivalence.

Ensign first class, at one point, had a specialized uniform insignia, a rank insignia worn on the Starfleet uniform of the 2270s, used until the 2350s. That uniform design was one of a rare few that had a specialized insignia in the ranking system of the era. (ST comic: "Who's Who in Star Trek, Issue 2")

The source reference Who's Who was written from the point-of-view of the mid-2280s, meaning there is no confirmation whether or not this insignia was continued in later uniform styles, as no other canon or licensed source mentions any reference at all to this rank.

	Enlisted ranks				Commissioned ranks							Flag ranks
Earth SF	CREW	PO2 PO1		CPO SCPO MCPO	ENS	LT		CMDR		CAPT FCAPT VICE CDORE		CDORE	RADM/2ADM	VADM/3ADM	4ADM	FADM/5ADM GADM
Starfleet & SFMC					ENS JG ENS ENS 1C	LT JG	LT	LT CMDR	CDR			CDORE 1ADM
	PVT	CPL	SGT MASTER SGT		2ND LT	1ST LT	CAPT	MAJOR	LT COL	COL		BRIG	GEN