Jeff the Killer is a story accompanied by an image of the title character. In the most notable version of the Jeff the Killer story which originated in 2011, a teenager named Jeffrey Woods is attacked by a group of bullies. The fight ends with Jeff being nearly arrested for assault, which his brother Liu takes the blame for, getting taken away to juvenile hall. This resulted in Jeff becoming depressed and introverted. His concerned parents force him to go to a party, where he gets approached by the same bullies he got in a fight with before. While he manages to kill the bullies, he is doused

with alcohol during the fight and is set on fire, suffering severe burns over most of his body. After being discharged from the hospital and having his bandages removed, Jeff begins to go insane when he sees the burns he suffered. He carves his own face to leave a smile-shaped scar, removes his eyelids, and kills his family. He becomes a serial killer. He kills by sneaking into houses at night and whispering "Go To Sleep" to his victims before killing them.

The story quickly became one of the most popular creepypastas and would inspire many other stories, including Jane the Killer. The character of Jeff was created by DeviantArt user "sesseur", the pseudonym of Jeff Case of Auburndale, Florida. The story above was not made by sesseur himself, but rather "a fan of his earlier work". Sesseur began posting about Jeff on Newgrounds in 2008 under the alias "killerjeff", describing a Bloody Mary-like a ritual which supposedly can be performed to summon Jeff. According to the original story, Jeff "accidentally spilled a bucket of acid on his face while trying to clean his bathtub". Also in original story, Jeff's real name is Jeffrey C. Hodek, not Jeffrey Woods

A 2013 article asserted that the original image of Jeff the Killer was an extensively edited picture of a girl who reportedly committed suicide in the fall of 2008 due to people online ridiculing her appearance. However, in 2018, after extensive research done by the users of 4chan's /x/ (Paranormal) board, this rumor was debunked; the earliest known instances of the image that was used in the creepypasta appearing online at the time had been found on the Japanese imageboard website pya.cc, dating back to September and November 2005. In 2022, an even earlier instance of the image was found dating back to July 2005 on the Japanese image sharing site fileman.ne1.jp. There exists a community dedicated to finding the unedited image that was featured in the original creepypasta