Multiple realities
(covers information from several alternate timelines)

These are unidentified humanoids species observed in the 23rd century.

Alien Starfleet Academy cadets Edit

Aliens with leather head-bands Edit

Aliens with leather headbands

Alien ambassadors

Ambassadors from this species served on the Federation Council in 2286. (Star Trek IV: The Voyage Home)

These suede costumes, tassels and resin jewelry were featured on the Zaranites seen in Star Trek: The Motion Picture.
According to a costume of one of these individuals that was auctioned off in the It's A Wrap! sale and auction, these individuals are Mazorites. [1]
According to an item description at the Propworx auction this hat belongs to the Kazarites. [2]

Alien with netting on face Edit

Alien with netting on face STVI

An alien at the Khitomer Conference

This alien was present with another of its kind, at the Khitomer Conference. (Star Trek VI: The Undiscovered Country)

Babel Conference attendees Edit

Discovery aliens Edit

Elysian councilor Edit

Enterprise (alternate reality) aliens Edit

Green-skinned boy Edit

Nimbus III inhabitants Edit

Port of San Francisco bar visitors Edit

Purple Federation members Edit

This race with light purple skin are prominent members of the Federation, having joined sometime prior to 2268. A delegate from this race attended the Babel Conference in 2268. (TOS: "Journey to Babel")

At least one member of this species was seated in the Federation Council in 2286. He had the characteristic purple skin color of his species, mildly purple hair and yellow irises. (Star Trek IV: The Voyage Home)

Members of this race were present at the Khitomer Conference in 2293. (Star Trek VI: The Undiscovered Country)

In the alternate timeline, a purple child passed Hikaru Sulu and Pavel Chekov as they disembarked the Enterprise and entered Starbase Yorktown. (Star Trek Beyond)

A close-up background shot of this character can be seen here.
In Star Trek Online this species was given the name "Violacean".

Rura Penthe personnel Edit

San Francisco bar aliens Edit

Shenzhou alien Edit

Shipyard Bar aliens Edit

Silvertube Amazette alien Edit

Three female members of the Silvertube, Amazette aliens were present at the Camp Khitomer conference in 2293. Another member of this species served as assistant of the Federation President. These silver haired women were members of the Federation. The woman who assisted the President was the only one who wore a grey hat. (Star Trek VI: The Undiscovered Country)

The president's assistant was played by regular TNG extra Lena Banks. The other three dignitaries were played by Roma Lee Tracy and two unknown actresses. They all received no credit for their appearance.
The name of the race, described as ""Silvertube," an Amazette alien", was directly from the actress.[3] She was shooting the scenes at the Brandeis-Bardin Institute and was chosen to portray the Federation President's assistant. She should play his "eyes", because in an early version the president was blind and she should guide him. However, the scene with her and the President was cut from the aired film. In the finished film, she was only seen in the background, but the cut scene was part of the theatrical trailer.

Wrigley's pleasure planet girlEdit

M-113 creature as Nancy to Darnell

The M-113 creature appearing as a girl from Wrigley's pleasure planet

This girl was once encountered by Crewman Darnell on Wrigley's pleasure planet. In 2266, an M-113 creature appeared to him in the form of this girl at the same time that it resembled Nancy Crater to Leonard McCoy, as he remembered having last seen her, and an older version of Crater to James T. Kirk. McCoy found Darnell's comment crass and said so.(TOS: "The Man Trap")

This girl was only mentioned in dialogue.

Yellow-skinned Alien with horizontal nose slits Edit

Yellow-skinned alien TUC

A member of the species

Yellow-skinned Alien side view

Side view

Two members of this species were present during the Khitomer Conference in 2293. This species had a peculiar way of clapping hands with outstretched arms. (Star Trek VI: The Undiscovered Country)

Played by an unknown performer.
According to special effects makeup artist Ed French, "The Khitomer peace conference was a fun scene, because most of the aliens in the audience were homages to past Star Treks and The Outer Limits. We made a number of aliens that were strongly influenced by Wah Chang, the makeup artist who created many of the creatures for those TV shows. We had a couple of aliens who were reminiscent of his Children of Spider Country makeups, as well as the Chameleon that Robert Duvall played." (Charting the Undiscovered Country: The Making of Trek VI, p. 90)