PSA: if you're a green card holder married to a US citizen, you may not have to wait 5 years to naturalize
Immigration attorney here. This one comes up constantly and a lot of people wait longer than they need to, so putting it in one place. The general rule to apply for citizenship is 5 years as a permanent resident. But there's a 3-year rule for people married to a US citizen, and a lot of eligible people don't realize they qualify. To use the 3-year timeline, generally all of these have to be true. You've been a permanent resident for 3 years. You've been married to and living with the same US citizen spouse for those 3 years. Your spouse has been a US citizen for that full 3-year period. And the marriage is bona fide, meaning a real, good-faith relationship. One point that surprises people: it doesn't matter how you got your green card. You don't have to have gotten residency through that spouse to use the 3-year rule. If you became a resident some other way and later married a citizen, you can still qualify once the 3 years line up. Everything else about naturalization stays the same, the English and civics test, good moral character, the interview. So if you're a resident married to a citizen, it's worth counting your dates before you assume you're on the 5-year clock.