 Issues concerning scientific explanation have been a focus of philosophical attention from Pre-Socratic times through the modern period. However, modern discussion really begins with the development of the Deductive-Nomological (DN) model. This model has had many advocates (including Popper 1959, Braithwaite 1953, Gardiner, 1959, Nagel 1961) but unquestionably the most detailed and influential statement is due to Carl Hempel (1942, 1965a, and Hempel &amp; Oppenheim 1948). These papers and the reaction to them have structured subsequent discussion concerning scientific explanation to an extraordinary degree. After some general remarks by way of background and orientation  (Section 1),  this entry describes the DN model and its extensions, and then turns to some well-known objections  (Section 2).  It next describes a variety of subsequent attempts to develop alternative models of explanation, including Wesley Salmon’s Statistical Relevance  (Section 3)  and Causal Mechanical  (Section 4)  models, Unificationist models due to Michael Friedman and Philip Kitcher  (Section 5),  and Pragmatic theories found in the work of van Fraassen  (Section 6).  Section 7 provides a summary and discusses directions for future work. This article thus discusses treatments of scientific explanation up to the end of the twentieth century. 