The Kurlans were the now extinct inhabitants of the planet Kurl.
Their culture believed that an individual person was in fact a community of individuals, each with their own voice, their own desire and their own view of the world. This belief was manifested in one of their forms of art known as a Kurlan naiskos.
The Kurlan history can be divided into several ages, among them the Third Dynasty (about 12,000 years ago) and the Fifth Dynasty. The Kurlans died out several millenia before the 24th century. (TNG: "The Chase")
In the novel Worlds of Star Trek: Deep Space Nine, Volume 2, it was revealed that the Kurlans were an ancient colony of Trills. It is revealed that the Kurlans genetically engineered the symbionts to not only be less dependent on their hosts but they could move from host to host as a matter of routine.