I am a foreign student in the U.S., and my boyfriend, a U.S. citizen, just proposed. We plan to get married and settle down in the United States. If he sponsors me, how long will it take before I get U.S. citizenship?
First, let’s get one important thing straight: Marriage to a U.S. citizen makes you eligible for a green card. Having a green card for a certain number of years can make you eligible for U.S. citizenship. But it’s a two-step process—at a minimum. In other words, even if your U.S. citizen husband sponsors you, you cannot become a U.S. citizen right away.
Below are the steps you will probably have to go through, and the typical amount of time each one will take.
NOTE to anyone who isn’t in the exact same situation: Procedures differ for applicants who are living outside the U.S., or who are inside the U.S. but not in lawful immigration status, or who are marrying a U.S. permanent resident rather than a citizen. See this chart for the procedural scenarios.
WARNING ABOUT TIME ESTIMATES: The below discussions of average USCIS processing times refer to "normal" circumstances. However, with the start of the coronavirus pandemic, there are no normal circumstances. As of early 2020, many USCIS offices were closed to the public, meaning you'll be unable to attend an in-person interview (as is required) until they reopen. Even then, ongoing delays are guaranteed.
If the marriage breaks up or you stop living together, you must count a full five years from the date of your approval for residence to apply to naturalize. And if your marriage runs into trouble or you get divorced before you’re able to get the conditions on your permanent residence lifted, you could be facing deportation as well. See What If Your U.S. Spouse Won't Sign the Joint Petition (I-751)?)
The news is also bad if the marriage ends due to the death of the U.S. spouse, as described in My U.S. Citizen Spouse Died: Can I Still Apply to Naturalize After Three Years?.
For comprehensive information on the green card application process, see Fiance and Marriage Visas: A Couple’s Guide to U.S. Immigration. Or, if you have any questions about complicating factors in your case, or wish help with the application process, consult an immigration attorney.