Lovecraft Country is a term coined by Keith Herber for the New England setting, combining real and fictitious locations, used by H. P. Lovecraft in many of his weird fiction stories, and later elaborated by other writers working in the Cthulhu Mythos. The term was popularized by Chaosium, the producers of the Lovecraftian role-playing game Call of Cthulhu. Lovecraft scholar S. T. Joshi refers to the area as the "Miskatonic region", after its fictional river and university, while Lovecraft biographer Lin Carter calls it Miskatonic County, though Lovecraft indicates that at least some of his fictional towns were located in the real-life Essex County of Massachusetts.
In its 1998 supplement Dead Reckonings, Chaosium defined Lovecraft Country as "a land located in the northeast of Massachusetts. The most important portion stretches along the Miskatonic River valley, from Dunwich in the far west to where it enters the Atlantic Ocean between Arkham, Kingsport, and Martin's Beach." These locations, along with Innsmouth, are a list of the most significant locations in Lovecraft Country.
Sometimes the phrase is used in a more inclusive sense, encompassing not only northeastern Massachusetts but also the southern hills of Vermont (the setting of The Whisperer in Darkness) as well as Lovecraft's hometown of Providence, Rhode Island, where he set such works as The Case of Charles Dexter Ward and The Haunter of the Dark.
Lovecraft first used a New England setting in his 1920 short story "The Terrible Old Man", set in Kingsport. "The Picture in the House" (written later in 1920), is the first of his stories to mention both Arkham and the Miskatonic Valley. The story begins with something of a manifesto for why the New England countryside is a fitting backdrop for his horror stories:
"the true epicure of the terrible, to whom a new thrill of unutterable ghastliness is the chief end and justification of existence, esteem most of all the ancient, lonely farmhouses of backwoods New England; for there the dark elements of strength, solitude, grotesqueness, and ignorance combine to form the perfection of the hideous." 
In a 1930 letter to Robert E. Howard, Lovecraft attempted to explain his fascination with New England as a setting for weird fiction: "It is the night-black Massachusetts legendary which packs the really macabre 'kick'. Here is material for a really profound study in group neuroticism; for certainly, none can deny the existence of a profoundly morbid streak in the Puritan imagination." 
Lovecraft first mentioned Arkham's Miskatonic University in "Herbert West–Reanimator", written in 1921-1922. He added Dunwich to his imaginary landscape in 1928's "The Dunwich Horror", and expanded it to include Innsmouth in 1931's The Shadow over Innsmouth.
Other Lovecraft stories that make use of Lovecraft Country settings include "The Festival", "The Colour out of Space", "The Strange High House in the Mist", "The Dreams in the Witch House", and "The Thing on the Doorstep".
August Derleth, Lovecraft's friend and literary executor, discouraged other Cthulhu Mythos writers from setting their stories in Lovecraft's New England. But he himself attempted to fill in the blanks of the setting, particularly in his posthumous "collaborations" with Lovecraft — actually Derleth's stories based on fragments, notes or ideas that Lovecraft left behind after his death.
The Lurker at the Threshold is set in Billington's Wood, a fictional forest north of Arkham, while "Witches' Hollow" takes place in the titular valley in the hills to the west of the town. The title of "The Fisherman of Falcon Point" refers to a promontory on the Atlantic coast south of Innsmouth. "Wentworth's Day" and "The Horror from the Middle Span" take place in the area north of Dunwich, while "The Gable Window" concerns a house on the Aylesbury Pike.
Between 1990 and 1998, Chaosium released a number of Lovecraft Country gamebooks for the Call of Cthulhu roleplaying game, series created by author/editor Keith Herber. Most were background supplements which codified descriptions of Lovecraft's named cities, but there were also a number of adventure books. These included:
- Arkham Unveiled (1990)
- Return to Dunwich (1991)
- Kingsport: The City in the Mist (1991)
- Escape from Innsmouth (1992)
- Adventures in Arkham Country (1993)
- Miskatonic University (1994)
- Tales of the Miskatonic Valley
- Dead Reckonings (1998)
- Before the Fall (1998)
- Children of the Deep (unreleased sequel that explored Innsmouth after its fall described in Escape from Innsmouth)
Some of the books have been rereleased in the 2000s (H.P. Lovecraft's Dunwich, H.P. Lovecraft's Arkham, and H.P. Lovecraft's Kingsport).
Skotos, an online game company, has licensed Chaosium's Lovecraft Country material. They have produced two games, Lovecraft Country: The Tomb of the Desert God and Lovecraft Country: Arkham by Night, as well as a comic, Lovecraft Country: Return to Arkham, written by Shannon Appelcline.
In 2008, following Chaosium's expanded licensing program for Call of Cthulhu, Keith Herber and Tom Lynch established Miskatonic River Press. The publisher's first release, New Tales of the Miskatonic Valley, which marked both Herber's return to Call of Cthulhu and Lovecraft Country was announced published in 2009.
The phrase Lovecraft Country is now used outside of the Cthulhu gaming community. Return to Lovecraft Country was a collection of short stories set in "the New England of H.P. Lovecraft", published by Triad Entertainments in 1996. The editor, Scott David Aniolowski, has also done editorial work for Chaosium. Eternal Lovecraft, a short-story collection published by Golden Gryphon Press in 1998, has a section called "Lovecraft Country". Lovecraft Country was the title of a 2016 novel by Matt Ruff.
The phrase occurs in popular discussions of Lovecraft's connection to the region. The Harvard Law Record used the phrase in an October 20, 2005 article:
Many Lovecraft stories take place in "Lovecraft Country"--the fictional North Shore towns of Arkham, Innsmouth, Kingsport, and Dunwich (perhaps fictional equivalents of Ipswich, Salem/Danvers, Marblehead, or Newburyport).
- More Annotated H. P. Lovecraft, S.T. Joshi and Peter Cannon
- Lovecraft: A Look Behind the Cthulhu Mythos, Lin Carter
- See "Shadow Over Innsmouth", "Dreams in the Witch House".
- Dead Reckonings, Kevin Ross & Shannon Appel eds.
- "H. P. Lovecraft's 'The Picture in the House'", The H. P. Lovecraft Archive.
- The Annotated Lovecraft, Joshi and Cannon, p. 2
- The Dunwich Horror, by H. P. Lovecraft. Lovecraft's original story featuring Dunwich.
- The Shadow over Innsmouth, by H. P. Lovecraft. Lovecraft's original story featuring Innsmouth.
- Skotos: Lovecraft Country
- "Spirit of Lovecraft Haunts Cambridge, New England", Dan Alban, The Record, October 20, 2005
- "A Short Tour of Lovecraftian New England", from The Cthulhu Mythos: A Guide
- Chaosium's (empty) Lovecraft Country Page
- Skotos' Lovecraft Country Game Pages
- Return to Lovecraft Country Book (ISBN 1-57502-535-3)
- Eternal Lovecraft Book (ISBN 0-9655901-7-8)
- Lovecraftian Sites in New England
- The Virtual World of H.P. Lovecraft, an ongoing mapping of Lovecraft's imaginary New England