The party hasn't held one since 1980, and that one peaked with the announcement that Kim Jong Il, the father of the country's current leader, would succeed Kim Il Sung, the regime's founder, as leader. He eventually took power in 1994, when the elder Kim passed away.
According to the party's own bylaws, the party congress is "the party's supreme organ" which means this political gathering is the highest authority of the most powerful institution in North Korea.
The ruling Workers' Party of Korea, or WPK, dominates everything in North Korea. It controls the government and military, along with much of North Korean society.
Party officials decide where you go to school, what job you have or whether you can trade in the growing private sector.
The congress opens May 6.
The primary reason for the party congress is to consolidate and institutionalize Kim Jong Un's power in the regime.
Since he took power over four years ago there have been many officials removed from office or rumored to have been executed, most recently Ri Yong Gil, chief of the North Korean Army's general staff.
So, the congress is an opportunity for Kim to press a reset button on North Korean political culture.
Party leaders made the decision to hold the congress last fall, well aware that they would conduct a fourth nuclear test and another rocket launch -- also aware of the international condemnation these actions would draw.
These proclaimed accomplishments have rallied support for the regime and create the ideal conditions for the party congress.
It is also no accident that they're having this major political meeting before U.S. presidential elections in November and the South Korean presidential elections in 2017.
What happens at the party congress?
The party congress focuses on two things: the WPK Charter and electing the party's power organizations.
The first order of business will be amending the charter, which is road map as to how the WPK relates to North Korea's population, government and society, how it views the world, and how it, as a political party, is organized and does business.
The congress will almost certainly elect its leading official, Kim Jong Un, and will then then elect members of the Central Committee, the party's leading collective authority.
The Central Committee will then meet on the sidelines of the party congress and elect people to the WPK's power organizations such as the Political Bureau and Central Military Commission. All these activities will be punctuated by reports and speeches.
Why is it important?
This will be the first party congress in over 35 years.
If North Korea wants to effect major changes, this is the forum in which to do it. However, this is unlikely to happen.
The congress will yield some clues and telltale signs about Kim Jong Un's goals for the country over the next five to 10 years.
There won't necessarily be any forthcoming substantive policy document, but during the congress' proceedings there will be some sense of how Kim wants to manage domestic policy and how North Korea will conducts its relations with foreign countries.
We are likely going to see some statements or rhetoric celebrating North Korea's rocket launches and its nuclear weapons program, as well as affirmation that it will continue research and development in these fields.
We will also see who will be holding senior political posts during the next few years, which will tell us who's in favor with Kim, who's retired and who's been cast off. Part of this might include a generational change, at least in midlevel WPK posts.
Attending this event will be functionaries, government officials, soldiers, police officers, factory workers and farmers who were elected by their local party organizations to attend.
There will be senior North Korean officials -- and one clue of who's kept their job and is still in favor will be who is sitting on the rostrum during the congress.
There is also the possibility that foreign delegations will attend.
Will North Korea conduct further nuclear or rocket tests before May 6?
The North Koreans enjoy keeping observers guessing.
There is a chance of a fifth nuclear test, a missile test or a large-scale live-fire military exercise.
It would be totally characteristic of Kim Jong Un's North Korea to begin a major political gathering with a bang.