Mario invites his friends Luigi, Peach, Toad, Yoshi, Wario and Donkey Kong to have a party. In the game which best can be described as a big board-game, Mario and friends compete in various mini-games.
 
There are 6 ordinary tables and 2 secret ones, each with a special "themes", one for each character:
Donkey's Jungle Adventure
Peach's Birthday Cake
Yoshi's Tropical Island
Wario's Battle Canyon
Luigi's Engine Room
Mario's Rainbow Castle
 
The game features over 50 different mini-games and four players can play simultaneously. This game isn't produced by Nintendo as one might think. It's Hudson who's behind this title.
   
Mario Party - Story (from the manual)
Mario looked around and smiled. Throwing a party had been an excellent idea. It had been a long time since they had all gotten together. All his friends were there:
Luigi, Peach, Toad, Yoshi - even Wario and Donkey Kong. They laughed and talked about all the adventures they had shared together in the past. But what was there to do now? The conversation turned to their dreams for the future. Amazingly, they all envisioned the same thing... To become a Super star upon whom everyone in the world could rely. Then Wario asked, "Which one of us is the biggest Super star?" "I am!" "It's me!" they all shouted. The gang couldn't come to an agreement because they each wanted to be the best. They needed to prove once and for all who truly was number one. Suddenly, Toad had an idea. "Isn't a Super star someone who helps others when they're in trouble?" Everyone realized he was right. Then Toad told them about a Warp Pipe in Mushroom Village that could take you anywhere you wanted to go. Surely there were people on the other side of that Pipe who needed their help. They all ran as fast as they could to Mushroom Village and jumped into the Warp Pipe. But none of them knew what exciting adventures awaited them on the other side...