The 7th Congress of Workers' Party began Friday in Pyongyang, the nation's capital and biggest city.
North Korean leader Kim Jong Un said the event will "lay out the brilliant blueprint that will advance the final victory of our revolution," according to the state-run newspaper Rodong Sinmun, CNN reported.
But the secrecy surrounding the event continues, even with the presence of more than 100 international media outlets.
About 3,000 party members have poured in for this once-in-a-generation political gathering, officials tell CNN.
The congress will be held at a convention center called April 25 House of Culture. While the building also hosted the previous party congress in 1980, it was not officially announced as this year's venue until the day before the gathering.
There will be plenty of spectacle as thousands of costumed North Koreans will parade and perform choreography in this scrubbed-down metropolis.
Political pronouncements are likely, though nobody is sure what Kim has in mind.
The congress is also likely to see Kim announce the continuation of North Korea's nuclear weapons program. That, along with military intelligence, is a major reason why many South Korean and US government officials believe a fifth nuclear test could happen at some point during the congress.
Kim's birth date is unknown, but he's thought to be in his early 30s, meaning he wasn't even alive when the last congress was held in 1980.
At that time, his grandfather, Kim Il Sung, North Korea's founder and president, elevated his son Kim Jong Il to No. 2 in the party, solidifying his position as successor. Kim Jong II took power in 1994 when his father died and never held a congress.