Quiz Castle (クイズキャッスル) is a Japanese online brand offering free quizzes and reference-style articles for people who enjoy testing their knowledge and discovering new topics. Its website brings together playable quizzes and an encyclopedia section, with featured and newly added content to explore. Quiz subjects include challenging readings of place names from regions such as Kyoto, Hokkaido, Tokyo, and Osaka, as well as regional dialects, difficult kanji, and station names.

The questions are designed to invite visitors to answer and see how much they know, with themes ranging from everyday language to local knowledge. For readers who want to learn beyond the quizzes, Quiz Castle publishes collections and rankings on topics such as Hakata and Hokkaido dialects, gaming and otaku terminology, card games, tongue twisters, business vocabulary, names, and jokes. The site combines light entertainment with accessible information, making it a destination for casual solo quiz play and browsing informative lists.

Its content is presented in Japanese and is organized around quizzes and articles that visitors can explore online