Bison King (Japanese: バイソンキング) is the personal mecha of the sixth ranger StarNinger (Kinji Takigawa) in Shuriken Sentai Ninninger (2015). In keeping with its pilot's American cowboy/Western-ninja theme, the robot follows a Wild-West sheriff motif. It is formed by combining two of his Otomo Nin: Rodeomaru, a turquoise humanoid that echoes the lead mecha Shinobimaru and acts like a mounted rider, and the Bison Buggy, a four-wheeled ATV-style buggy with bison styling. In the Power Rangers adaptation Ninja Steel / Super Ninja Steel (2017–2018) the same design appears as the Gold Ranger's (Levi Weston) Bull Rider Megazord, combined from the Robo Rider Zord and the Ninja Bull Zord.

The transformation ("Bison Change") is triggered when StarNinger inserts and spins the "Bison" Otomo Nin Shuriken in his Ninja StarBurger. Rodeomaru detaches from the Bison Buggy, whose body splits so that the rear wheels fold forward into the legs/feet and the front wheels become the shoulders, while the oversized Shuriken sits atop Rodeomaru as the head behind a deploying faceplate. Its principal weapon is the Bison Rifle, fitted with a short bayonet blade for close combat. Both components can alternatively merge with the series' main mecha Shurikenjin to form the larger King Shurikenjin.

The DX toy was released in April 2015 by Bandai (Japan) as "Shuriken Gattai DX Bison King" (RRP ¥6,800). It comprises the two separate units, Rodeomaru and the Bison Buggy, which reconfigure into Bison King with only a few parts (saddle, rifle and Shuriken) being repositioned. Construction is predominantly plastic with sparse paint applications; there is no meaningful die-cast content. An electronic gimmick reads the mounted Otomo Nin Shuriken to detect whether Bison King or King Shurikenjin is being formed and plays the matching voice and sound effects. For the Power Rangers line, Bandai America issued the same mold in 2017 as the "DX Bull Rider Megazord" (roughly 27 cm / 10.5 in), functionally identical but in Ninja Steel colors and without the Japanese callouts. No Hasbro version exists, as Hasbro only took over the Power Rangers toy license from 2019 onward.