柳井市是山口县东南部室津半岛东岸的市，辖区内半数以上地区为丘陵地，主要市区集中在海岸附近的平地上。

在中世纪时期，柳井港为濑户内海内的主要港口，并为周防国的海上交通要冲，并成为商业的中心。

在江户时代属于岩国吉川家（岩国领）的领地。

Yanai(柳井市,Yanai-shi) is a city located in Yamaguchi Prefecture, Japan. The city was founded on March 31, 1954.

The interchange and the expressway is located in the east. Yanai is bounded by Hikari.

As of March 1, 2011, the city has an estimated population of 34,634 and a population density of 248 persons per km². The total area is 139.90 km².