At the most basic level, the requirement to become a historian is to acquire expertise in one or more historical fields, usually through some combination of education and training. Like all academic professions, history offers a variety of levels of expertise, but the minimum requirement is usually a master's degree in history.
To work as an academic historian at a university or college, a Doctorate of Philosophy, Ph.D., is usually required. This involves a long process of study (usually five or more years) that usually includes one or more years of coursework, language study, field research and the writing of a book-length dissertation or thesis that contributes original knowledge to a historical field.
There are also options for those without the time, inclination or ability to pursue a Ph.D. One of these options is to pursue a Master's degree in a historical field. Master's degrees often open up paths in museums, historical societies and other history organizations. They involve one or two years of course work as well as a component of research and thesis writing. Many historians who wish to work in museums also pursue training in Public History or Museum Studies, to make them more prepared for the unique opportunities and challenges of working in museums.