Operation Auca was an attempt by five Evangelical Christian missionaries from the United States to bring Christianity to the Waodani or Huaorani people of the rain forest of Ecuador. The Huaorani, also known pejoratively as Aucas (a modification of awqa, the Quechua word for "savages"), were an isolated tribe known for their violence, against both their own people and outsiders who entered their territory. With the intention of being the first Christians to evangelize the previously uncontacted Huaorani, the missionaries began making regular flights over Huaorani settlements in September 1955, dropping gifts, which were reciprocated. After several months of exchanging gifts, on January 3, 1956, the missionaries established a camp at "Palm Beach", a sandbar along the Curaray River, a few kilometers from Huaorani settlements. Their efforts came to an end on January 8, 1956, when all five—Jim Elliot, Nate Saint, Ed McCully, Peter Fleming, and Roger Youderian—were attacked and speared by a group of Huaorani warriors. The news of their deaths was broadcast around the world, and Life magazine covered the event with a photo essay.

The deaths of the men galvanized the missionary effort in the United States, sparking an outpouring of funding for evangelization efforts around the world. Their work is still frequently remembered in evangelical publications, and in 2006 was the subject of the film production End of the Spear. Several years after the death of the men, the widow of Jim Elliot, Elisabeth, and the sister of Nate Saint, Rachel, returned to Ecuador as missionaries with the Summer Institute of Linguistics (now SIL International) to live among the Huaorani. This eventually led to the conversion of many, including some of those involved in the killing.