This chapter describes the experience of the Tunguska event and considers the question of how it should be understood as a disaster. It begins by surveying events around the world from the perspective of a space object hurtling toward the Earth in the early twentieth century. This background sets the stage for the blast of 1908 and introduces some of the characters who will later feature prominently in the book. Telling the story of a group of Indigenous Evenki witnesses close to the epicenter, the chapter considers the experience of the explosion, the initial interpretations of it, and the influence of Soviet ethnography on what can be known. Analyzing observer testimony, it discusses Tunguska as a social and ecological disaster and shows how the concept of vulnerability can be extended to cosmic catastrophes.