If you're a foreign student in the United States, you're no doubt interested in making sure you're here legally, and that you won't need to look over your shoulder to see whether you're about to be arrested by U.S. immigration agents and deported. But there's a lot of confusion about how long a student's legal stay lasts, so let's address that here.
When you first received your F-1 student visa, the U.S. consular officer would have put a stamp into your passport for U.S. entry. However, this visa stamp is truly only an entry document. The date there does not determine the allowable length of your legal stay in the United States. In fact, if that date passes and your visa expires, you do not necessarily need to leave the United States, assuming you are maintaining valid student status.
The date an F-1 student is actually expected to leave the United States is another matter. It (commonly referred to as your "period of authorized stay") is indicated on the I-94 Record of Arrival and Departure issued by Customs and Border Protection (CBP) upon entry. While tourists and most other visitors to the U.S. on nonimmigrant visas receive an actual date on their I-94, indicating exactly when their legal status expires, F-1 students receive a "D/S." D/S stands for "duration of status."
According to U.S. government regulations, a student can remain in the U.S. in F-1 status for the duration of the period during which the student is "pursuing a full course of study at an educational institution approved by USCIS for attendance by foreign students, or engaging in authorized practical training following completion of studies, plus 60 days to prepare for departure from the United States." (See 8 C.F.R. § 214.2(f).)
So, as long as you are otherwise maintaining your F-1 status (for instance, you haven't dropped out of school or taken a job), you are allowed to remain in the United States until the end of your 60-day grace period.
This allows students flexibility in pursuing their studies. For example, if you decided to change from a Master's degree to a Ph.D. halfway through a program, your Form I-20 could be updated and extended to give you the extra time you need to complete the new degree without you having to leave the United States.
In any case, you are certainly not required to renew your F-1 entry visa in order to maintain status within the United States.
If you travel outside the United States after your F-1 visa expires, but you haven't yet completed your studies, you will need to apply for a new visa stamp before you can reenter in F-1 status. This shouldn't be a big deal, assuming no major changes in your financial and academic situation. You will go to your local U.S. consulate to request this, as explained next.
The only way to get a new visa stamp is to apply for one at the United States embassy or consulate in your home country. The process will be similar to the one you went through to get your initial visa stamp.
You will have to again demonstrate that you have the intent to return home when you complete your studies and that you have liquid assets with which to fund your studies and living expenses. You will also have to show that you have been maintaining your F-1 status by making normal progress towards your academic degree.
Always check the website for your embassy or consulate for additional information about the application process.
A lot of students ask about applying for a new visa stamp in a convenient third country, such as Canada or Mexico. You might have this option, but it is normally not a good idea to use it. There is always the risk that your application will be delayed. This will be problematic if you do not have the authorization to remain in that third country for an extended period of time.
Legally speaking, you are maintaining your F-1 status as long as you are enrolled as a full-time student and are making normal progress towards completing your degree. You are also maintaining your F-1 status if you are approved for Optional Practical Training (OPT) after you complete your program.
It is important to know some of the more common reasons for falling out of F-1 status, as many can easily be avoided. These include, but are not limited to:
Most of these occurrences can be avoided if you meet with your DSO as soon as you become aware of an issue. For example, you should know whether or not you are ill and need to reduce your course load, or you need more time to complete your degree before your Form I-20 expires. Once you are aware of this possibility, make arrangements with your DSO for a timely extension.