Yiali lies on the southwestern part of Aegean. It stands right after Kos and before Nisyros, approximately  7 kilometers away in which administratively belongs to. Yiali belongs to Dodecanese complex and has an area of about 5 square kilometers. The population is considered to be after the last census about 20 inhabitants.

Yiali island has been declared as a landscape natural beauty and as such there are forests of pine and arbutus, blue limpid waters and sandy beaches.

Yiali is a volcanic island and it has two lava dome one at the northeast side and the other at the southwest side, both are connected by a narrow isthmus. The volcano is inactive of course.

Pumice and perlite are being mined on Yiali. In the ancient times though another ore was mined , one that has been used for making usefull tools. This ore was the obsidian which is abundant in the northern part of the island.

The specific geographical coordinates of Yiali island is 36°39’36.8″N 27°06’42.6″E in Aegean Sea.