It depends a little on what they are writing. In general they are "writers". If they write books they are usually called "authors", if they write poems they are usually referred to as "poets", if they write newspaper colums they are "journalists" etc.
That person is an author
A Person WhoWrites Stories for Newspapers Is A Journalist
An author, or writer, or novelist.
A writer, author, or poet.
Journalists, authors, and newspaper columnists.
The person who writes literature is called a writer (poet, novelist,master of short story,teller,scenarist in movie making field)
An author. If he or she exclusively write poems, the word would be 'poet'.
A composer writes the music. A lyricist writes the words.
A person who writes a news article is called a journalist.
the person who writes software programs called Programmer
what do we call a person who writes history books NEW RESPONDENT. Historian.
A person who writes the libretto for an opera is simply referred to as the librettist.
The person who makes a will (or 'testament') is a testator.