Yamaguchi 3rd district (山口県第3区) is a single-member electoral district for the House of Representatives, the lower house of the National Diet of Japan.

It is located in Western Yamaguchi Prefecture and includes Shimonoseki the largest city in the prefecture.

Before redistricting in 2022, Shimonoseki and Nagato had been a part of the abolished Yamaguchi 4th district.