First published in 1912, "The Lost World" is a science fiction novel by British writer Arthur Conan Doyle concerning an expedition to a plateau in the Amazon basin of South America where prehistoric animals still survive.
"The Lost World" explored the idea that prehistoric life might still exist in unexplored areas of the globe. Part science fiction, part adventure story, the novel marks a significant shift in Doyle's writing, as he temporarily put aside the famous Sherlock Holmes to introduce professor Challenger, a physical, rude, bear-like man who would feature in several subsequent works.

The novel opens with Edward Malone ("Ned") finding his declarations of love rejected by Gladys, for she can only love a heroic man. Malone, a newspaper reporter, has been assigned to write an article on professor Challenger who has returned from South America with unbelievable stories of prehistoric life in a remote location in the Amazon. The scientific community in London thinks Challenger is a fraud, so the professor plans a new excursion to bring back concrete evidence of his claims. He asks for volunteers to join him, and Malone steps forward in hopes the trip will prove his heroic nature to Gladys. They will also be joined by the wealthy adventurer Lord John Roxton and the skeptical professor Summerlee, who hopes to prove Challenger truly is a fraud.
After a dangerous journey up the rivers and through the forests of the Amazon, the four adventurers arrive at the massive plateau where they soon encounter a pterodactyl, forcing Summerlee to admit that Challenger had been telling the truth...

"The Lost World" has had a significant influence on science fiction, inspiring works including Michael Crichton's The Lost World, the related Jurassic Park movies, and The Lost World television series.