Gui Minhai, also known as Michael Gui, is a Hong Kong-Swedish book publisher and writer. He is an author of many books related to Chinese politics and Chinese political figures; Gui authored around 200 books during his ten-year career under the pen-name Ah Hai (阿海) and is one of three shareholders of Causeway Bay Books in Hong Kong.

Causeway Bay Books is an independent bookstore in Taipei, Taiwan, which until December 2015 was an upstairs bookstore located in Causeway Bay, Hong Kong. The first bookstore in Hong Kong was popular with tourists from mainland China looking for books on Chinese politics and politicians which were not available in mainland China. In late 2015, five people associated with the store disappeared, sparking international concern. The first bookstore closed after the disappearance of its last staff member, Lee Bo, in December 2015. A second version of the bookstore was opened in Taipei, Taiwan in April 2020 by Lam Wing-kee, the founder of the original Hong Kong store and one of the five people who disappeared.