Hiroshi Hiroyama is a Japanese comic artist, illustrator, and manga creator known for his work on the Fate franchise. He is also recognized by the pseudonym KALMIA, under which he initially created Fate-related dōjinshi before achieving mainstream success.

Hiroyama is the original creator of the manga series Fate/kaleid liner Prisma Illya. The series began serialization in Kadokawa Shoten’s Comp Ace magazine in September 2007, serving as an alternate universe spin-off of the visual novel Fate/stay night by Type-Moon. The original manga concluded in November 2008 and was followed by a direct sequel, Fate/kaleid liner Prisma Illya 2wei!, which ran from April 2009 to March 2012. A third series, Fate/kaleid liner Prisma Illya 3rei!!, began serialization in May 2012 and continues to be published.

As the original creator, Hiroyama’s work on these manga series formed the basis for a significant multimedia franchise. His credits on the subsequent anime adaptations are consistently as the original creator or original character designer. The first anime series, produced by Silver Link, aired in 2013, followed by several sequel series and films that adapted the storylines of his manga: Fate/kaleid liner Prisma Illya 2wei! in 2014, Fate/kaleid liner Prisma Illya 2wei Herz! in 2015, and Fate/kaleid liner Prisma Illya 3rei!! in 2016. He is also credited for the original story in the OVA Fate/kaleid liner Prisma Illya: Prisma Phantasm and the theatrical film Fate/kaleid liner Prisma Illya - Licht Nameless Girl.

Beyond the Prisma Illya series, Hiroyama’s artistic identity is closely tied to the Fate franchise. He has provided illustrations for works such as Fate/EXTRA CCC Extra Garden and has served as a character illustrator for the mobile game Fate/Grand Order, where he is credited for the designs of characters including Illyasviel von Einzbern, Chloe von Einzbern, Miyu Edelfelt, and Mochizuki Chiyome. His career began within the dōjinshi community, and he has continued to release dōjinshi works alongside his commercial projects.

In the industry, Hiroyama is significant for successfully reinterpreting the dark fantasy world of Fate/stay night into a magical girl genre narrative while maintaining a distinct artistic identity. His work has received praise from key creators of both the Fate series and other influential magical girl franchises, establishing a lasting expansion of the Type-Moon universe.