Regional Presidential Primaries Act of 1985 - Prohibits any State from conducting a presidential primary election except in accordance with the provisions of this Act. Establishes six regional primaries to be held in each presidential election year. Sets the dates for such primaries. Sets requirements for voter eligibility in the primaries conducted under this Act. Authorizes the Attorney General to bring a civil suit in United States district courts when he has reason to believe that a State is holding a primary in violation of this Act. Requires presidential candidates in a primary, in order to be eligible to receive payments from the Presidential Election Campaign Fund, to agree to enter at least one State primary in each of the six regions and to notify the Federal Election Commission which primaries will be entered. Authorizes necessary appropriations.