Brian Michael Thomsen (April 13, 1959 – September 21, 2008) was an American science fiction editor, author, and anthologist.

Thomsen was raised in the New York City neighborhood of Rockaway Beach and attended Regis High School in Manhattan.

In the 1980s, TSR had developed a reputation for underpaying its authors compared to the major fiction publishers in New York.

Mary Kirchoff, who eventually came to lead the Books Department, had spearheaded changes to increase author compensation so as to better retain talent.

After Wizards of the Coast purchased a bankrupt TSR in 1997, Thomsen was fired from his position, Mary Kirchoff was rehired, and Wizards set about reversing the bonds broken in Thomsen's tenure, notably including luring Salvatore back to work with the Forgotten Realms again.