Demon possession is a staple of the horror genre. I stuck with the purest forms of possession for this list, but there are movies about possessed cars, dolls, and even hair extensions!
Books:

The Exorcist by William Peter Blatty is a classic, I couldn’t leave it off the list! I personally liked the book better than the movie – a lot of the movie didn’t make much sense to me until I had read the book.

My Best Friend’s Exorcism by Grady Hendrix is more of a fun take on possession, with lots of 80s nostalgia thrown in.

A Head Full of Ghosts by Paul Tremblay is told by the younger sister of a girl who is believed to be possessed, as a reality film crew comes in to document it. As in most of the stories on this list, this book will leave you questioning whether “possession” is a mental illness, or if there is some darker force at work.
Movies:

The Exorcism of Emily Rose (2005) is based on the true story of an exorcism gone wrong and the subsequent court case. While the story unfolds slowly, there are truly creepy moments and it leaves you with a lingering sense of dread.

The Possession (2012) is fairly unique among possession movies because it’s based around Judaism rather than Catholicism.

The Last Exorcism (2010) takes a mockumentary approach, as an exorcism who no longer believes takes a camera crew along for his final exorcism.
Almost all of these stories follow the Possession formula, which usually features a young girl. What do you think: is this formula overdone?