The Ullians were a humanoid race native to the Ullian homeworld. They were telepaths with a vested interest in learning the memories of other species, with the power to enhance and recover lost memories.

Before the 21st century, the Ullians were a violent people. Telepathic memory invasion was a common occurrence. By the end of the 21st century, they had become peaceful, and instances of memory invasion were virtually eliminated, although some members of Ullian society still practiced that form of rape.

By 2368, the Ullians had embarked upon an ambitious plan to construct a library of memories from species across the Federation and beyond. Several Ullians, including Tarmin and Jev, were trained in telepathic memory retrieval and used the ability to reconstruct and collect memories. It was hoped the memory library would be not unlike an repository of oral histories. One group of Ullians visited eleven planets in eight star systems including Melina II, Nel III, and Hurada III. Kaldra IV was also a planned stop. Before the Ullian delegation arrived at Kaldra IV, Jev was found guilty of committing telepathic memory invasion against several members of the USS Enterprise-D crew, bringing a temporary interruption to the research.

For the most part, the Ullians are a gentle, honest, and friendly people. They have a great passion for their work, but do not wish to coerce other species into participating if they are not willing.

The Ullians are physically similar to Humans. The sides of their skulls have a pronounced hairless bulge, most likely related to their telepathic centers.

Ullians are capable of telepathically reading most humanoid species, although other telepathic species such as the Betazoids have difficulty in reading Ullian minds.