The Blue Emperor of Oz is an Oz fiction written by Henry S. Blossom and illustrated by Mogo Brown, and published by the author in 1966, in a limited edition of 300 copies. It was the first piece of fan fiction published about the Land of Oz. Blossom dedicated the book to Robert R. Pattrick.
The book is subtitled Being a true and faithful chronicle of the discovery that there exists a Blue emperor in the land of Oz, and what became of him and his faithful drinking mug, Hiccup.
Blossom wrote undeterred by the fact that he infringed on copyrights. He used the character Jam as his protagonist, a character created by Rachel Cosgrove in 1951 and protected by copyright (then and now). Also, most of L. Frank Baum's original Oz books were still protected by copyright in 1966.
(Blossom was hardly a ruthless literary pirate; his correspondence about his book is extant and was sold at auction in 2006. Blossom wrote to Maxine Reikhoff, then the children's books editor at Reilly & Lee, soliciting permission to publish his book; he also corresponded with Ruth Plumly Thompson, Harry Neal Baum, Eloise Jarvis McGraw and others. Thompson, at least, was supportive.)
In the story, Jam finds the head of the Gump in an antique shop, which provides him a means to return to Oz. With the help of Kabumpo he rescues Princess Ozma's grandfather Ozroar, the Blue Emperor of the title, who was kidnapped by Mombi and turned over to a villainous magician. (Like later fan fictioneers, Blossom relied on hints and minutiae in the Oz books to inspire his story. Ozma's grandfather is mentioned in Ozoplaning with the Wizard of Oz; the Blue Emperor is mentioned in The Purple Prince of Oz and The Silver Princess in Oz.)
Blossom was the first to apply the names of Oz authors spelled backwards to his characters — including his own: there's a Mossolb in his story, along with a Muab and a Namyl. Some later Oz authors have followed his example, notably Chris Dulabone in The Deadly Desert Around Oz.
Armstong State College Press of Savannah, Georgia issued a second edition of the book, edited by Patricia Robinson-King, in 1982.
The name Ozroar was suggested by Fred M. Meyer. It has been picked up and used by later Oz writers.