Gosei Knight (ゴセイナイト, Gosei Naito) is a mysterious warrior of which Gosei World has no record. He comes to identify with the Goseigers.
Ten-thousand years ago, he was originally the Groundion Headder (グランディオンヘッダー, Gurandion Heddā) and battled the Yuumajuu until he got separated from his Gosei Angel allies. Ending up in a glacier, Groundion made a pact with the planet itself as it gives him the means to assume his human-like form to fight the revived Yuumajuu and cleanse the Earth of any threat to it. His motivations however have put him at odds with the current Goseigers, as he doesn't care for the people who inhabit the Earth. However, the more time he spends on Earth fighting alongside the Goseigers, the more he begins to realize that their missions are one in the same.
Unlike the Goseigers, Gosei Knight uses the mysterious Knightick Power (ナイティックパワー, Naitikku Pawā), enabling him to use the abilities of the Skick, Landick, and Seaick Tribes. When fighting, he refers to himself as "The Earth purifying knight of destiny! Gosei Knight" (地球を浄める宿命の騎士！ゴセイナイト, Hoshi o kiyomeru shukumei no kishi! Gosei Naito). Before performing his finishing attack, he calls upon the Conviction of Knightick Power (断罪のナイティックパワー, Danzai no Naitikku Pawā). Gosei Knight debuted in Epic 17.
- Robo Knight - Power Rangers counterpart in Power Rangers Megaforce.