Trinity Blood is a Japanese light novel series written by Sunao Yoshida with illustrations by Thores Shibamoto, composed of two series, the short-story 'R.A.M.' and the full-length novel 'R.O.M.', published by Kadokawa Sneaker Bunko across 12 volumes.

The novel series was left unfinished due to the sudden death of author Sunao Yoshida, cutting short the planned storylines including a final confrontation between Abel and his brother Cain.

By August 2008, the domestic (Japanese) volumes of Trinity Blood had sold about 1.5 million copies, while overseas editions (Korea, Taiwan, USA) had sold around 50,000 copies combined.

In a 2006 poll for 'Kono Light Novel ga Sugoi!', the character Abel Nightroad ranked 8th in the male character category.

Before the anime adaptation, a radio drama based on R.A.M. volumes 1-3 was broadcast on fmosaka's 'Kadokawa Sound Cinema' program with a different voice cast than the later anime, and was released on 9 CDs total via VAP.

The three Nightroad siblings are named Abel, Cain, and Seth, directly referencing the sons of Adam and Eve in the Book of Genesis.

Many antagonists in the Rosenkreuz Orden are named after the Three Wise Men from the Nativity story (Balthasar, Melchior, and Caspar von Neumann), and the thirteen Inquisitors of the Inquisition Bureau are named after the twelve apostles (plus one implied to reference Judas).

Several characters were explicitly modeled on real people: Leon Garcia de Asturias' appearance was based on actor Antonio Banderas, Havel's design was modeled on former Argentine footballer Gabriel Batistuta, and Brother Pietro's design was based on Gaburetto Gyabure from the anime 'Heavy Metal L-Gaim'.

Havel's name is a reference to Václav Havel, the Czech pro-democracy activist and first president of Czechoslovakia.