Movement is a core property of human language which has been a major focus of study since the inception of the generative enterprise. This Element is concerned with the syntactic movement of heads. On the basis of data from an array of languages, it demonstrates that there are two types of syntactic head movement, describes their properties, and develops a unified theory of both types in terms of the structure building operation Merge. One of the two types of head movement (essentially "long head movement") falls out within a minimalist approach to syntactic structure building once it is recognized that in this framework there is no principled distinction between heads and phrases. The other type of head movement (essentially "head-to-head substitution") also falls out under a certain set of assumptions about labeling/projection and the nature of lexical items.