A special Poké Ball that is used during the Bug-Catching Contest.
When the player participates in the Bug-Catching Contest, they receive 20 Sport Balls exclusively for use within the contest. They are not placed in the player's Bag, and any unused Sport Balls are returned at the end of the competition.
In The Bug Stops Here, Ash and Casey participated in a Bug-Catching Contest, receiving a Park Ball each to be used during the competition. Casey used her Park Ball to catch a Weedle, while Ash caught himself a Beedrill. Eventually, Ash's catch won him the contest, earning him a Sun Stone and his new Beedrill as prizes, with the Beedrill being placed inside a regular Poké Ball.
In its Pokémon Global Link artwork, the Sport Ball has an S marking on the upper half. In the games, it instead has a Poké Ball symbol in its place.
In Generation II, the Park Ball's name is written as one word on the in-battle menu during the Bug-Catching Contest, where it takes the place of the Pack command. However, when the ball is used, its name is formatted properly.