Yes, you may qualify if you were already married to a U.S. citizen when they died.

You filed Form I-130 before your spouse passed away or you file Form I-360 Widower’s Petition within 2 years of their death.

If you’re in the U.S., you may still qualify for adjustment of status Form I-485.

If abroad, you may proceed through consular processing with a valid I-360 approval.

If your spouse was a green card holder not a U.S. citizen, your options are more limited, but you may still qualify under special circumstances e.g. humanitarian grounds.

Yes, in some cases you can still apply for a green card as a widow(er) if the marriage was bona fide and you apply within two years of your spouse’s death.