James Herbert Brennan (5 July 1940 - 1 January 2024) was an Irish lecturer and the author of over 100 fiction and non-fiction books for adults, teens and children, as well as several role-playing games.

Brennan was born to grocers James and Sarah Brennan and grew up in Gilford, Co. Down, Northern Ireland. He became interested in mysticism at an early age, an interest that would remain with him the rest of his life. At age 18, he became a journalist with the Belfast Telegraph. In the 1960s, he moved to Dublin to become the editor of a weekly magazine titled Scene.