First One was the title given to the ruling male and female of Ligon II.
Hagon and Yareena were First Ones in 2364. The former First One, Lutan, was superseded by Hagon at the behest of Yareena. According to the customs of their world, the male First One stood behind and to the left of the female First One and the Second One behind and to the right. (TNG: "Code of Honor")