When can I apply for citizenship after marrying a US citizen?

Yes, file -i-130.

You may not apply for citizenship. You must first apply for the green card, and be approved of it. After green card approval, you can apply for citizenship after 2 years and 9 months, provided that you are still married to the same spouse who petitioned you for the green card. In the event of a divorce, you will have to wait 4 years and 9 months to apply for citizenship after the green card is approved. A common misconception is that if you have a child or married for a long time, citizenship will be granted automatically. In reality, to apply for citizenship, you must have the required physical presence (lived in the US long enough), continuous residence (not left the US for more than 6 months in the past 5 years), good moral character (no criminal history, filed tax return yearly, paying child support, etc). You will also have to pass a civic test before you can become a US citizen. In sum, if you have a green card for more than 2 years and 9 months, you can apply for citizenship now, based on the information you provided. If you have more questions please feel free to contact my office.