The unauthorized or undocumented resident immigrant population is defined as all foreign-born non-citizens who are not legal residents. Most unauthorized residents either entered the United States without inspection or were admitted temporarily and stayed past the date they were required to leave.

Unauthorized residents applying for adjustment to lawful permanent resident (LPR) status under the Immigration and Nationality Act (INA) are unauthorized until they have been granted lawful permanent residence (a green card)—even though they may have been authorized to work. Persons who are beneficiaries of Temporary Protected Status (TPS) are not technically unauthorized.

In Oregon, as in all states, the definition and treatment of unauthorized or undocumented resident immigrants are primarily governed by federal law, specifically the Immigration and Nationality Act (INA). Unauthorized immigrants are those who have entered the United States without proper inspection or have overstayed their visas. While Oregon state law does not change the federal definition of unauthorized immigrants, the state has enacted policies that may impact this population. For example, Oregon allows unauthorized immigrants to apply for driver's licenses and state-funded financial aid for college. However, when it comes to adjusting status to become a lawful permanent resident (LPR), unauthorized immigrants must follow the federal process outlined by the INA. This process includes various eligibility criteria and often requires an immigrant visa to be available. Until they adjust their status and are granted a green card, these individuals remain unauthorized, even if they have been granted work authorization or are beneficiaries of Temporary Protected Status (TPS), which provides temporary relief from deportation but does not confer lawful permanent resident status.