The Deltans were a humanoid species originating from the Federation planet Delta IV.
Deltans were identified by their bald scalps. They had pain-relieving abilities that manifested during tactile contact. This ability did not, however, heal injuries. Deltans believed Humans to be a sexually immature species. Because of their high sexuality, Deltans had to swear an oath of celibacy upon entering service in Starfleet, as a promise not to take advantage of any fellow crewmember.
In 2141, the ECS Horizon encountered a group of Deltans. Travis Mayweather, who was fifteen at the time, later described them as very attractive and very open. On the advice and invitation of his father, he dealt with the feelings they engendered in him by performing exhausting workouts in the gym, a method he returned to (and recommended to Lt. Malcolm Reed) while three Orion slave girls were "guests" aboard Enterprise in December 2154.