Super Saiyan 4 Kaio-ken (超サイヤ人4界王拳 Sūpā Saiya-jin Fō Kaiōken, lit. "Super Saiyan 4 World King Fist" or "Super Saiyan 4 Fist of the King of the Worlds") is a combination of the Super Saiyan 4 transformation and the Kaio-ken technique.
Like the variation of the technique utilizing Super Saiyan Blue, the user utilizes the Kaio-ken technique whilst in their Super Saiyan 4 form. Usage of this technique produces an equally similar double aura effect of its own, with the flame-like golden aura of the Super Saiyan 4 surrounded by the jagged and violent crimson aura of the Kaio-ken. When used by Gogeta, it results in his hair turning bright orange.
In the Dragon Ball Z Collectible Card Game, Super Saiyan 4 Goku can use Kaio-ken.
Xeno Gogeta as a Super Saiyan 4 can use the Kaio-ken technique in Super Dragon Ball Heroes.
After the 1.15.00 update in Dragon Ball Xenoverse 2, Goku as a Super Saiyan 4 can briefly use the Kaio-ken technique by performing various techniques such as Kaioken Kamehameha, x4 Kaioken Kamehameha, Kaioken Assault and Kaioken x20 Kamehameha in his custom moveset.
- Unused voice lines in Xenoverse 2 suggest that Gogeta was intended to be able to use the Kaio-ken while in Super Saiyan 4.
- DBXV2 Unused Voice Files. YouTube (July 15, 2017).