The eternal leaders of North Korea are mentions of deceased leaders of North Korea. The phrase was mentioned in a line of the preamble to the Constitution, as amended on 30 June 2016, and in subsequent revisions.
It reads (in the original version):
Under the leadership of the Workers’ Party of Korea, the Democratic People’s Republic of Korea and the Korean people will uphold the great leader Comrade Kim Il Sung as the eternal President of the Democratic People’s Republic of Korea and Comrade Kim Jong Il as the eternal Chairman of the National Defence Commission of the Democratic People’s Republic of Korea...
In 1972, the presidency was established, and Kim Il Sung was elected to the position by the Supreme People's Assembly, the North Korean legislature, on 28 December 1972. Kim served as president until 1994 when he died, and the position was left vacant and his son and successor Kim Jong Il was not given the title.
"Eternal President"
The preamble of the Constitution of the Democratic People's Republic of Korea as amended on 5 September 1998 reads:
Under the leadership of the Workers' Party of Korea, the Democratic People's Republic of Korea and the Korean people will hold the great leader Comrade Kim Il-sung in high esteem as the eternal President of the Republic...[2]
After the death of Kim Jong Il, the constitution was amended in 2012, declaring him Eternal General Secretary of the Workers' Party of Korea and Eternal Chairman of the National Defence Commission.
In 2016, the title "eternal leaders of Juche Korea" was introduced by amending the preamble of the constitution, which was given to Kim Il Sung and Kim Jong Il.
Head of state role in North Korea after the deaths of Kim Il Sung and Kim Jong Il
North Korea portal 
