Castle Amber is a Dungeons & Dragons adventure module designed by Tom Moldvay. This was the second module designed for use with the Expert D&D set. The module is in part an adaptation of Clark Ashton Smith's Averoigne stories, and set in the fictional medieval French province of that name.

In Castle Amber, player characters explore the haunted mansion of the Amber family and encounter new monsters. They are drawn into a cursed castle surrounded by a deadly mist and must navigate the demented and often hostile inhabitants to find a hidden portal to the world of Averoigne. Breaking the curse requires finding the inter-dimensional tomb of Stephen Amber. The module is inspired by the Averoigne stories of Clark Ashton Smith, Edgar Allan Poe's works, and Roger Zelazny's The Chronicles of Amber series. Castle Amber was first published in 1981 and was ranked the 15th greatest Dungeons & Dragons adventure by Dungeon magazine in 2004.

The player characters explore the haunted mansion of the Amber family, and encounter new monsters such as the brain collector. The module is an adventure scenario set in a castle surrounded by an unusual gray mist.

During their night's rest on their way to Glantri, the player characters are unexpectedly drawn into a large castle surrounded by an impenetrable, deadly mist. This is the result of a curse the wizard-noble Stephen Amber (Etienne d'Amberville) put on his treacherous relatives for murdering him.

The only way to escape Castle Amber (or Château d'Amberville) is to explore the castle, putting up with the demented, and at times insane, members of the d'Amberville family and the other, often hostile, denizens, and open a hidden portal to the wilderness of the world of Averoigne, where the party can find the means to reach the inter-dimensional tomb in which Stephen Amber rests, in order to break the curse and return home.

In this world, magic is frowned upon, and spellcasters may come to the attention of the Inquisition.

The module's credits give special thanks to Clark Ashton Smith and Casiana Literary Enterprises, Inc., "for use of the Averoigne stories as inspirational material." Castle Amber (Château d'Amberville) draws from the Averoigne stories of Clark Ashton Smith. The main non-player characters of the module, the Amber family (d'Amberville in French, as an option), are not actually in any of Smith's stories, and were created by the designer to provide a link to Averoigne. A selected bibliography is included at the rear of the module.

In addition to the Averoigne references, there are individual encounters within the module that have allusions to stories written by others.^{[citation needed]}