Xenophobia
Xenophobia was a psychological, anti-species condition, the fear and hatred of anyone or anything unknown, foreign, alien, or anything that was other than oneself. Someone who suffers from xenophobia was referred to as xenophobic, or a xenophobe.

Xenophobic races encountered by both  and the  included the Tholians. (; ) 

In 2154, xenophobia was at heightened levels on Earth in the aftermath of the Xindi attack. While visiting San Francisco, Denobulan Doctor Phlox was confronted by an angry bar patron who didn't like him, resulting in a bar-room brawl. () The Xindi attack also fueled the xenophobic Terra Prime movement. () 

In the mirror universe, the Terran Empire was an extremely xenophobic government that considered aliens innately inferior to s. They led a crusade to conquer and enslave all non-Terrans that lasted from the late-22nd century to at least the 2260s. (, , )

According to Captain James T. Kirk, during the First Contact encounter with the First Federation in 2266, "the greatest danger facing us is ourselves, an irrational fear of the unknown. But there's no such thing as the unknown, only things temporarily hidden, temporarily not understood." ()

According to Agmar, the Phylosians were "a peaceful race" that had "a fear of aliens." ()

In 2367, the crew of the  had encounters with several xenophobic species including the Paxans and Malcorians. () The people of Kaelon II were considered isolationists, almost to the point of being xenophobes. ()

The Prytt were extremely xenophobic and desired no contact with the  that they shared their planet with, or any other civilization. () 

The Bajoran Alliance for Global Unity believed that Bajor belonged to the Bajorans and that all other races were inferior and thus should be expelled from their planet. Their emergence in 2370 lead to several attacks on Deep Space 9. ()  

The Dominion, created by the Founders, was built entirely on xenophobia. The Founders' main aim was to bring their style of order to what they saw as the chaotic nature of solids throughout the universe. ()

The Cardassians had a tendency towards xenophobia. When scientists working on behalf of the Cardassian Central Command conducted a genetic engineering experiment designed to create more powerful soldiers by (among other things) amplifying this tendency, the results proved disastrous. Several soldiers were left behind when the Cardassian Union abandoned space station Empok Nor. ()

Species 8472 was highly xenophobic, which was only strengthened by their war with the Borg. This is evident in their philosophy, which determines only the strong (themselves) may survive while the weak (everyone else) must perish. ()

The Devore were perhaps the most xenophobic species in the Delta Quadrant, especially towards telepaths. ()

The Varro were a xenophobic species and the Ba'Neth were also extremely xenophobic. (; )

Commander Chakotay once noted that many of the species encountered in the Delta Quadrant by the crew of the  could be considered xenophobic. Thus, he was pleased at the value placed on openness and freedom by the species of the Markonian outpost, even if opening up the ship to them meant increased levels in crime. Captain Kathryn Janeway agreed with the sentiment. ()

See also
 Prejudice
 Racism
 Recluse

Xenophobic movements
Alliance for Global Unity (Bajor)
Logic extremist ()
Terra Prime (Earth)
Vulcan Isolationist Movement ()

External link
 

de:Xenophobie
Psychological conditions