You are allowed to apply for citizenship after 5 years of holding a Permanent Resident Green Card, or after 3 years if you’re filing as the spouse of a U.S. citizen. Despite the five years (or 3 years) of permanent residence requirement, you are actually allowed to submit your naturalization application to the U.S. Citizenship and Immigration Services (USCIS) within the 90-days leading up to the end of your 3- or 5-year wait period as a Green Card holder.