Korean nationality (Korean: 한국국적) refers citizenship of the Korea. Korean citizen (Korean: 한국인) refers citizen of the Korea. Korea is divided into two distinct sovereign states, North Korea (Democratic People's Republic of Korea) and South Korea (Republic of Korea). Nowadays, there are three kinds of Korean nationality: South Korean nationality, North Korean nationality, and Chōsen-seki (ethnic Koreans in Japan who have neither Japanese nor South Korean citizenship).
Most people who have Korean nationality are ethnic Koreans. South Korea and North Korea were created within months of each other in 1948, both claimed sovereignty over all of Korea. So South Korea and North Korea regards South Koreans and North Koreans are their citizen. However, the South Korean government distinguishes Chōsen-seki people from other Koreans in Japan for some treatments.
Korean nationality is awarded to being born to either a Korean national father or Korean national mother (Jus sanguinis). However, In North Korea, if a child is born abroad to one North Korean citizen parent and one of mixed nationality, the citizenship is to be determined by the parents. Both Koreas adopt exceptional Jus soli, or the "right of the soil," regulation. A child born in Korea with "unknown or stateless parents" is automatically granted Korean nationality.