Nihiliphobia

From Memory Alpha, the free Star Trek reference

Nihiliphobia was a psychological condition that was also known as the fear of nothingness. Symptoms included dizziness, nausea, and unspeakable dread.

Many of the crew of the USS Voyager began exhibiting signs of the condition when they were forced to cross the Void, a massive region of space unpopulated by cosmological phenomena. Neelix was especially susceptible. The Doctor claimed to have suffered from nihiliphobia during the first months of his extended operation. (VOY: "Night")

Phobias
Agoraphobia • Aquaphobia • Claustrophobia • Nihiliphobia • Transporter phobia • Xenophobia