What's countries lie on the Korean Peninsula?

North Korea and South Korea

Explanation:

The Korean Peninsula is made up of the countries of North and South Korea. Initially, Korea was a single country just after the second world war when it was split into two. The Northern part being domiciled by the North Korea and the Southern part flanked by South Korea.

The boundary between the two countries is one of the most militarized places on earth. The DMZ, De-Militarized Zone is a narrow piece of land that divides both countries nearly into two. Seoul is the largest city on the Korean Peninsula