Dayos IV was a planet, the fourth planet in the Dayos star system. This was the home of Ylda. (TLE novel: Excelsior: Forged in Fire)
In 2363, Kang, son of K'naiah met Ylda on Dayos IV. Kang fed and clothed her and told her of his son, as well as Kor's and Koloth's sons, all who had been killed by her husband, the Albino. (DS9 episode: "Blood Oath")
As part his cover while infiltrating the Orion Syndicate, Miles O'Brien's alias Connolly spent two years in prison of Dayos IV for dealing in stolen goods. (DS9 episode: "Honor Among Thieves")
- Dayos IV shares a similar name and location to Daros IV.