The motivation, derivation, and properties of some unitary transformations of the Dirac equation are discussed, including the Foldy–Wouthuysen, Cini–Touschek, and Melosh transformations as members of a general class of such transformations. In addition, some spin‐1 considerations are outlined, as well as a way of dealing with free massless electrons and Maxwell’s equations in a format parallel to rest‐system considerations.