Documents Required For Your Cruise
Before embarking on a cruise each passenger is required to have not only a cruise ticket, but certain other documents, depending on the itinerary of the ship. The following list is provided as a guideline to these requirements for U.S. citizens. Non-U.S. citizens should check with the embassy or consulate of their respective countries to verify those requirements.

PROOF OF CITIZENSHIP
A passport is the preferred document for all cruises, although not required for certain destinations (see below).  To obtain a passport, you'll be required to complete a Passport Application and provide a Birth Certificate and twoidentical photos as specified on the application. Passport Applications can be obtained from your local U.S. Passport Office, on the internet at http://travel.state.gov/passport_services.html or by calling the National Passport Information Center at 1-888-362-8668 ($4.95 per call flat rate fee, must use credit card) or 1-900-225-5674 (35 cents per minute for automated information or $1.05 per minute for operator assisted calls).
For those cruises that stop ONLY in Alaska, the Bahamas, Bermuda, Canada, Mexico and the Caribbean, passengers may use aCertified Birth Certificate AND a government-issued photo identification in lieu of a passport.

If no passport is available, a certified birth certificate is required for EVERY passenger, regardless of age.  A copy may be obtained from the Bureau of Vital Statistics in the state of birth and is identified by a raised seal.  Some states now offer wallet-sized plastic copies, which are also acceptable. 

A photo ID is also required for any passenger age 18 and over.  A driver's license is the most common form of identification.  Those who do not have a driver's license may, in most states, obtain a photo ID from the state licensing office.  A phone call to the local office is recommended to verify what is required to obtain this ID card. 

Some cruises to the Caribbean and Panama Canal that stop in certain countries in South and Central America may require a passport. The cruise line or your travel agent can advise you if your itinerary has this requirement.

EXACT LEGAL NAMES (first and last) must be shown on cruise documents.  This must match the name shown on your passport or photo ID and birth certificate. It is assumed that a married woman's last name will be different, but in the event your first name on the photo ID is not the same as that on the birth certificate, you should advise your travel agent.  Middle names alone and nicknames are not allowed.

VISAS are required for U.S. citizens to visit certain countries (including, but not limited to Australia, Russia and Turkey). The cruise line will usually provide the necessary forms for each passenger to complete to obtain these visas.  In some cases, the cruise line will only require the passenger to provide them with passport information and a "blanket" visa will be issued for all passengers on the ship.  You should always verify with your travel agent what will be required for your specific cruise.
For MINORS (under the age of 18) traveling without parents, other documents may be required by the cruise line and/or the countries being visited.  For example, Mexico requires a notarized affidavit signed by ANY parent not accompanying the minor.  If only one parent is going on the trip, the other parent must sign a release form.  If neither parent is going, then BOTH parents must sign. 

It's always advisable, and in some cases required by the cruise line, for anyone taking a minor without his/her parents to have a notarized release form signed by the parents. This document would be especially important if the minor should require medical attention while on the cruise.
These guidelines are as accurate as possible at the time of writing, but regulations are always subject to change, so this information is not guaranteed.  It is recommended that you always verify the requirements of your cruise with your travel agent or cruise line.  You may also obtain additional information regarding travel regulations by checking the internet site listed above for passports.

Helpful Links
US Customs Service US
CDC information
Passport Applications US
Dept. of Agriculture
Travel Warnings