Jacob Franklin Mentzer III (born in 1950), is an American fantasy author and game designer best known for his work on early materials for the Dungeons & Dragons (D&D) fantasy role-playing game. He was a performing folk musician from 1968 to 1975, and played one concert at the White House during the administration of Richard Nixon. He has been closely involved with the world's largest game auction at the GenCon game convention since 1983, and is an expert* on (and a major collector of) family boardgames and role-playing games. (*See Game Buyers Price Guide, below.)
Mentzer was an employee at TSR, Inc. in the early stages of the company from 1980 to 1986. In 1981 he founded the Role-Playing Games Association (RPGA). Among other positions he held at TSR, he was Creative Advisor to the Chairman of the Board, Gary Gygax.
Mentzer's D&D-related publications include:
- The 1983 boxed sets of revised core rules for Dungeons & Dragons, Basic Rules Set 1 (red box) and Expert Rules Set 2 (blue box), along with their sequels Companion Rules (1984), Master Rules (1985), and Immortals Rules (1986). See the Editions of Dungeons & Dragons article for details on these boxed sets.
- Adventure module T1-4 The Temple of Elemental Evil, co-authored with Gygax in 1985
- Accessory module AC4 - The Book of Marvelous Magic (TSR, 1985), also co-authored with Gygax.
- The entire RPGA series of adventures based on Mentzer's own home "Aquaria" D&D campaign, coded R1 through R10. The R series of adventures was originally intended to form the basis of a new "Aqua-Oerdian" boxed set to expand upon the World of Greyhawk campaign setting, but these plans were shelved after Gygax left TSR in 1985.
- Module I-11, Needle (TSR, 1987).
- Module I-12, Egg of the Phoenix with Paul Jacquays (TSR 1989), a revised compilation of R1 - R4.
- Module IM-1, The Immortal Storm (TSR, 1986).
His works have been translated into at least 11 languages, and his 1983 - 1986 boxed sets of core D&D rules sold millions of copies worldwide. In addition to those best-sellers, he also wrote:
- Adventure module 2001: A Space Odyssey (based on the book by Arthur C. Clarke) for TSR's Star Frontiers game.
- The Game Buyers' Price Guide 1986 (with various contributing editors), summarizing the various hobby games and their prices (at the time; annual editions were planned but never produced).
He has also authored materials for Gygax's Fantasy Master series, as well as the Cyborg Commando role-playing game (published by New Infinities Productions Inc., aka NIPI), which he helped develop along with Gygax and Kim Mohan.
Mentzer left the game industry after the demise of Gygax's NIPI. His few publishing credits thereafter include:
- Cooking Without Fire with Paul Kamikawa (1992)
- "Trust at the Gaming Table", in the Origins Award-winning Game Master Secrets Vol. II (Grey Ghost Press, 2003)
- "The Baker's House" Web site.