Gregory L. Mahan was born in Richardson, Texas, but spent his formative years in the greater Houston area. Gregory fell in love with the works of Andre Norton at a very young age, and soon became a voracious reader of science fiction and fantasy works. He began crafting stories for his friends and family at the age of 8 when he asked for (and received!) a typewriter as a Christmas gift.

Gregory is known for the Llandra Saga series of epic fantasy novels, as well as several Celtic music tunebooks and a how-to guide on brewing mead. He has been a member of the Authors Guild since 2014.

In addition to writing, he enjoys Celtic music, and has played the Irish penny whistle and low whistle since 1995. His first band, Echoes of Ireland, was featured on KPFT radio's Irish Aires program, as well as being one of the bands chosen to play for Charles Sheehan, Consul General of Ireland on his visit to Houston in 2003. Gregory maintains one of the oldest and largest Irish music repositories on the internet, The Wandering Whistler Music Archives, and published his first songbook, Fifty Great Celtic Jigs, in 2002. In 2003, he joined the band Paddy Gone Wild, and was prominently featured on their CD, The Greatest Hits, released in 2008.