Yes, you can generally apply for naturalization even if your green card has expired, as long as you are otherwise eligible. Your permanent resident status does not expire when the card does. However, you will need proof of your status, and USCIS may require you to renew your green card or obtain temporary evidence during the process.

Some applicants choose to file Form I-90 to renew their green card before or alongside the N-400 to avoid delays. While not always required, having a valid card can make the process smoother, especially for identity verification and biometrics. Planning ahead can help reduce complications.