Not to be confused with Star KO.

Knockout Stars are "medallions" for KOing opponents in the Versus Mode or online play of Super Smash Bros. Melee, Super Smash Bros. Brawl, Super Smash Bros. 4, and Super Smash Bros. Ultimate, displayed at the bottom of each player's character selection screen panel. The amount of KO Stars received is dependent on the amount of times a KO is dealt. For example, if a player knocks out two opponents, or if they KO the same opponent twice, they will receive two KO Stars. Melee allows players to have a maximum of only 255 KO Stars at a time. Any KOs achieved after players have attained have 255 KOs will not reward them with a KO Star. In Brawl onwards, this limit is extended to 999 KO Stars.

The design of KO Stars have changed in each new iteration of the game. In Melee and Brawl they are yellow 5-pointed stars (Melee's has a more pronounced shadow than Brawl's) that increase in number up until 5, any more and it will be a single star with a tallied number to its right. for Nintendo 3DS uses a single white star along with the numerical value, regardless of how many KOs. for Wii U completely omitted a numerical value and added designs with colors and accents that were tallied into groups. Ultimate shows a medallion with a star in it, always showing the number of KOs like in for Nintendo 3DS.

KO Stars are reset to zero once the players exit the mode or (prior to Ultimate) change their name. CPU players do not earn KO Stars.