Dragonlance Chronicles Trilogy by Margaret Weis & Tracy Hickman
Parasol Protectorate Series by Gail Carriger
Sherlock Holmes Series by Arthur Conan Doyle
Amelia Peabody Series by Elizabeth Peters
Leviathan Trilogy by Scott Westerfeld
Vatta's War Series by Elizabeth Moon
The Sellswords Trilogy by R.A. Salvatore
Shandril's Saga by Ed Greenwood
Finder's Stone Trilogy by Kate Novak and Jeff Grubb
The Moonshae Trilogy by Douglas Niles
Shadow of the Avatar Trilogy by Ed Greenwood
Councilors & Kings Trilogy by Elaine Cunningham
The Empyrean Odyssey Trilogy by Thomas M. Reid
Ice Age Cycle by Jeff Grubb
The Dreaming Dark Trilogy by Keith Baker
The Blade of the Flame Trilogy by Tim Waggoner
The Dragon Below Trilogy by Don Bassingthwaite
Heirs of Ash Trilogy by Rich Wulf
Legacy of Dahkaan Trilogy by Don Bassingthwaite
The Chronicles of Abraxis Wren Duology by Paul Crilley
Dragonlance Legends Trilogy by Margaret Weis & Tracy Hickman
The Dark Disciple Trilogy by Margaret Weis
Kang's Regiment Duology by Margaret Weis
Defenders of Magic Trilogy by Mary Kirchoff
Elven Exiles Trilogy by Tonya C. Cook and Paul B. Thompson
Dragons of a New Age Trilogy by Jean Rabe
War of the Ancients Trilogy by Richard A. Knaak
The Dreamers by David Eddings
Mage Storms Trilogy by Mercedes Lackey
Tommy and Tuppence Series by Agatha Christie
Ariadne Oliver Series by Agatha Christie
The Passing of the Techno-Mages Trilogy by Jeanne Cavelos
Eureka Trilogy by Chris Ramsay
The Riyria Revelations Series by Michael J. Sullivan
Lindy Haggerty Series by Shelley Freydont
The Infernal Devices by Cassandra Clare
Duklyon: Clamp School Defenders Duology by CLAMP
The Emperor's Edge Series by Lindsay Buroker
Ladies of Distinction Series by Jen Turano
Wish Series by CLAMP
Blank Slate Series by Aya Kanno
Something I've discovered, I've not completed nearly as many series as I thought. Used to be that I'd skip around in the series (you can totally do that when you read as many mysteries as I use to) and never complete any of them. This was really awesome though, I love that there are so many complete fantasy series/trilogies on this list.