Your United States passport is an official identification document. It is issued by the United States Department of State and allows you to enter and leave the US. Your passport is your most important document when you travel outside the country. It shows that you are eligible to re-enter the US and allows you to seek help from a consulate or embassy if you run into problems aboard. Your passport also proves your identity.
Even though you will always want to keep your passport in a safe place and apply for passport renewal before any trip, sometimes when you want to renew a passport you realize that your United States passport has been lost, stolen, or damaged. If you realize at any time that you have a lost passport or a stolen or damaged one, it is vital that you report the problem and submit a US passport application or the appropriate passport renewal forms for a new US passport. Traveling without your passport is very dangerous and can make it difficult or impossible to re-enter the US. As well, under Section 1543 of Title 22 of the U.S. Code you may be in violation of US laws if your passport is damaged or violated. If your passport is stolen, you could easily become the victim of identity theft. For all these reasons, you will want to address a stolen, lost, or damaged passport at once.
If you realize that your passport has been lost or stolen while you are outside the country, visit the closest embassy or consulate immediately in order to seek help and in order to get travel documents issued to you immediately. Most US consulates and embassies have procedures for dealing with lost and stolen US passports and should be able to help you quickly.
If you are in the US and notice that your passport has been lost, stolen, or damaged, you will need to apply to a passport office in person to renew your passport. If your passport is lost or stolen, you will need to report that so that it cannot be used by someone else. If your passport is damaged, bring the passport with you. You will need to complete form DS-11 to replace your passport. If your passport is lost or stolen, you will need to complete form DS-64 as well as form DS-11 because you will need to apply for a new passport. In either case, you will need to provide proof of your identity, citizenship, and will need to provide photos as well as other documentation for your new passport.