autobiographer - someone who writes their own biography

hagiographer, hagiographist, hagiologist - the author of a worshipful or idealizing biography

author, writer - writes (books or stories or articles or the like) professionally (for pay)

Plutarch - Greek biographer who wrote Parallel Lives (46?-120 AD)

Giles Lytton Strachey, Lytton Strachey, Strachey - English biographer and leading member of the Bloomsbury Group (1880-1932)