A foreigner who is a permanent resident of the country in which he or she resides but does not have citizenship. To fall under this classification in the U.S., you need to either currently have a green card or have had one in the last calendar year. You also fall under the U.S. classification of resident alien if you have been in the U.S. for more than 31 days during the current year along with having been in the U.S. for at least 183 days over a three-year period that includes the current year.

Resident and non-resident aliens have different filing advantages and disadvantages. For example, a resident alien can use foreign tax credits, whereas a non-resident cannot. However, in general, a resident alien is subject to the same taxes as a U.S. citizen, while a non-resident alien only pays tax on income that is generated within the U.S, not including capital gains.