The term Reagan Democrat is used (with caution) by psephologists and (more freely) by political commentators to describe a phenomenon in American politics whereby, from a date sometime between 1965 and 1984, a significant portion of the electorate which had traditionally supported the Democrats defected to the Republicans, at least in Presidential Elections.

This process is held to account for the size of the majority of the popular vote enjoyed by Ronald Reagan in the 1984 Presidential Election. Possible causes advanced for the shift in voting patterns include a backlash against desegregation in the southern states, an increase in employment in smaller, non-unionised private sector enterprises, and the growth in the influence of lawyers, teachers and other professionals at the expense of that of manual workers within the Democratic Party.