Unearthed Arcana (abbreviated UA)[1] is the title shared by two hardback books published for different editions of the Dungeons & Dragons fantasy role-playing game.

The book was notorious for its considerable number of errors, and was received negatively by the gaming press whose criticisms targeted the over-powered races and classes, among other issues.

The designers did not reproduce material from the original book, but instead attempted to emulate its purpose by providing variant rules and options to change the game itself.

The original Unearthed Arcana was written by Gary Gygax with design and editing contributions by Jeff Grubb and Kim Mohan, respectively, and published by TSR in 1985.

He proposed the book as "an interim volume to expand the Dungeon Masters Guide and Players Handbook", as the information was spread out in several places and difficult to keep track of.

[4] Unearthed Arcana was to include material previously published in Dragon, written by Gygax and updated and revised for the book.

[7] Dragon editor Kim Mohan, with ideas from Gygax, Frank Mentzer, and Jeff Grubb, addressed the many errors found in the book.

[12] This reprint is the first printing of the book to be modified using the errata previously published in Dragon magazine incorporated into the corrected text.

[5] The section for the Dungeon Master includes suggestions for handling player characters, tables for social class and rank, new magic items, rules for combat without weapons, and gods for nonhumans.

[10] The second book to use the name Unearthed Arcana was written by Andy Collins, Jesse Decker, David Noonan, and Rich Redman, and published in February 2004 by Wizards of the Coast, for use with the Dungeons & Dragons third edition rules.

[23] The book ends with a checklist of the included variants, preceded by a short chapter discussing ways of transitioning among multiple games using different rulesets (one of which explicitly emulates the "Eternal Champion" stories of Michael Moorcock).

[27] Starting in January 2018, Unearthed Arcana content was generally added to D&D Beyond approximately one week after it was released on the official D&D website.

[30][31][32] In August 2023, Crawford stated that since originally launching Unearthed Arcana they have "received more than 500,000 surveys from players based on their time spent with the" playtest content.

"[14] Paul Cockburn reviewed the original Unearthed Arcana in issue 73 of White Dwarf magazine (January 1986), rating it 4 out of 10 overall.