An expert in or student of history, especially that of aparticular period, geographical region, or socialphenomenon: - Oxford Dictionary
Those who have full training and accreditation, who write critical analyses that elicit cause-and-effect relationships, who write for a specialist audience, and who publish primarily through academic presses should be called ‘historians’. – somegreymatter
historian, historiographer (a person who is an authority on history and who studies it and writes about it) – wordnet.princeton.edu
Although "historian" can be used to describe amateur and professional historians alike, it is reserved more recently for those who have acquired graduate degrees in the discipline. Some historians, though, are recognized by publications or training and experience
1. Herman, A. M. (1998). Occupational outlook handbook: 1998-99 edition. Indianapolis: JIST Works. Page 525.
What is a Historian?
Each historian defines his or her job, profession or calling differently. But all historians study and interpret the past. -
http://www.chashcacommittees-comitesa.ca/
Answer
There are thousands of historians at work today, but they work in a wide variety of jobs and ways. Fundamentally, to be a historian you need to love digging into the raw materials of history and an enthusiasm for sharing what you find. But how and where someone works as a historian makes for a wide variety of stepping stones to a career.
To do history in a professional way generally requires an advanced degree in history or a closely related field. Historians who work at colleges and universities, for instance, typically need a doctoral degree to get a job. – teachinghistorians.org