Penny was born in Toronto in 1958. Her mother was an avid reader of both fiction and non-fiction, with a particular liking for crime fiction, and Louise grew up reading mystery writers such as Agatha Christie, Georges Simenon, Dorothy L. Sayers, and Michael Innes.
Penny earned a Bachelor of Applied Arts (Radio and Television) from Ryerson Polytechnical Institute (now Ryerson University) in 1979. After graduation, at age 21, she embarked on an 18-year career as a radio host and journalist with the Canadian Broadcasting Corporation. At the start of her broadcasting career, Penny took postings at locations far from friends and family, and to help deal with feelings of loneliness and isolation, she increasingly turned to alcohol. At age 35, she admitted to an alcohol problem, and has been sober since. Shortly afterward, she met her future husband, Michael Whitehead, head of hematology at Montreal Children's Hospital, on a blind date.
After her marriage, Penny left the CBC to take up writing. She started a historical novel but had difficulty finishing it, and eventually switched to mystery writing. She entered her first novel, Still Life, in the "Debut Dagger" competition in the United Kingdom, placing second out of 800 entries. The novel won other awards, including the "New Blood" Dagger award in the United Kingdom, the Arthur Ellis Award in Canada for best first crime novel, the Dilys Award, the Anthony Award and the Barry Award for Best First Novel in the United States.
Penny continues to write, garnering major crime novel award nominations for almost every one of her novels and subsequently winning several of those awards.
Her work features Chief Inspector Armand Gamache, head of the homicide department of the Sûreté du Québec. The novels are set in the province of Quebec but feature many hallmarks of the British whodunit genre, including murders by unconventional means, bucolic villages, large casts of suspects, red herrings, and a dramatic disclosure of the murderer in the last few pages of the book.
In 2009, Penny helped to launch a new award for aspiring Canadian mystery writers, the Unhanged Arthur for Best Unpublished First Novel.
Penny currently lives in Knowlton, a small village in Quebec's Eastern Townships about 100 km from Montreal. Her husband Michael died on September 18, 2016.
In 2013, she was made a Member of the Order of Canada "for her contributions to Canadian culture as an author shining a spotlight on the Eastern Townships of Quebec".
For several years, Penny resisted selling the TV or movie rights to her books, afraid of losing creative control of her characters. However, when approached by PDM Entertainment and Attraction Images and offered a position as executive producer during film production, she changed her mind and agreed to sell them the rights to her first two novels. Still Life went into production in the fall of 2012, with British actor Nathaniel Parker cast as Chief Inspector Gamache. The movie aired on CBC TV in 2013.Still Life (2005) – Winner of the New Blood Dagger award, the Arthur Ellis Award, the Dilys Award, the 2007 Anthony Award, and the Barry Award
A Fatal Grace (Alternate title: Dead Cold) (2007) – Winner of the 2007 Agatha Award
The Cruelest Month (2008) – Winner of the 2008 Agatha Award; nominated for the 2009 Anthony, the 2008 Macavity Award, and the 2008 Barry Award
The Murder Stone (A Rule Against Murder in U.S.) (2009) – Nominated for an Arthur Ellis Award
The Brutal Telling (2009) – Winner of the 2009 Agatha Award, and the 2010 Anthony Award
Bury Your Dead (2010) – Winner of the 2010 Agatha Award, the 2011 Anthony Award, the 2011 Macavity Award, the 2011 Arthur Ellis Award, and the 2011 Nero Award
A Trick of the Light (2011) – Nominated for a Macavity, an Anthony Award, and an Agatha Award
The Hangman (2011) – novella
The Beautiful Mystery (2012) – Winner of the 2013 Macavity Award for Best Mystery
How the Light Gets In (2013) – Nominated for an Edgar Award and an Agatha Award
The Long Way Home (2014)
The Nature of the Beast (2015)
A Great Reckoning (2016)
Glass Houses (2017)