

In addition to the standard trade paperbacks, Hellboy stories are collected in oversized hardcovers known as library editions, and paperback omnibuses. In addition to the comics, the Hellboy novels written by author Christopher Golden are also considered in-continuity. Pre-Cavendish stories tend to be primarily short, stand-alone stories. Post-Cavendish stories are usually very continuity heavy, and require the reader to be relatively familiar with Hellboy's history. There are generally two types of Hellboy stories Pre-Cavendish (stories set chronologically before the first miniseries Hellboy: Seed of Destruction) and Post-Cavendish (stories set chronologically after the first miniseries). The series, focused on the titular Hellboy, spawned the Hellboy Universe. It is also sometimes informally called the "Mignolaverse". The Hellboy Universe currently spans over eighty trade paperbacks.

Its first appearance was in a black-and-white, four-page promotional comic by Mike Mignola with a script by John Byrne published by Dark Horse Comics in San Diego Comic-Con Comics #2 (August 19, 1993), distributed at the San Diego Comic-Con. The Hellboy Universe is the fictional universe of the Hellboy comic and its various spinoffs, created by Mike Mignola.
