Mary Ann Sims (born August 28, 1960), known professionally as Dinah Cancer, is an American singer.

She is the lead vocalist of 45 Grave, which helped found the deathrock music genre.

[1] She returned to using her birth name, Mary Sims, becoming a preschool teacher and running the Ragnarok occult bookstore.

Cancer said via her MySpace page: "I'm building this to keep the spirit of 45 Grave alive, introduce its magic to new fans, and as a personal commemorative of my best memories being the driving force and front person of 45 Grave".

The reformed 45 Grave (featuring Rikk Agnew and later Frank Agnew) performed the title track to the 2009 horror film Night of the Demons, and released their second studio album, Pick Your Poison, in 2012 on Frontier Records.