Kamen Rider Thouser (仮面ライダーサウザー) is a Kamen Rider from Kamen Rider Zero-One.

Gai Amatsu (天津 垓) is the CEO of ZAIA Enterprise's Japan Branch. He sees himself as the rival of Hiden Intelligence, and tries to one-up the company at every turn.

Kamen Rider Thouser is created to be a "better" Zero-One, and is accessed using the Amazing Caucasus (アメイジングコーカサス) Progrise Key, Awaking Arsino (アウェイキングアルシノ) Zetsumerise Key and the ZAIA Thousandriver (ザイアサウザンドライバー). His main weapon is the Thousand Jacker (サウザンドジャッカー), a spear that can absorb the data of other Progrise Keys and use them for attacks.

First appearance: Kamen Rider Reiwa: The First Generation (cameo), Kamen Rider Zero-One Episode 17