The K-3 visa is a type of non-immigrant visa for a foreign-citizen spouse of a United States (U.S.) citizen. This visa allows foreign-citizen and U.S. citizen spouses to have the option to obtain a nonimmigrant K-3 visa overseas and enter the United States to await approval of the immigrant visa petition, thereby reducing the separation time between spouses. K-3 visa recipients will then subsequently need to apply to adjust status to a permanent resident (LPR) with the Department of Homeland Security (DHS), U.S. Citizenship and Immigration Services (USCIS) upon approval of the petition.
The spouse of a U.S. citizen applying for a nonimmigrant K-3 visa will need to ensure that there is an immigrant visa petition filed on their behalf or her behalf by his / her U.S. citizen spouse. Pending approval, a K-3 applicant should meet a number of the immigrant visa requirements. Under U.S. immigration law, "a foreign citizen who marries a U.S. citizen outside the U.S. must apply for the K-3 visa in the country where the marriage took place."
Eligible children of K-3 visa applicants receive K-4 visas. Both K-3 and the K-4 visas allow their recipients to stay in the United States while immigrant visa petitions are pending approval by USCIS.
A "spouse" is defined as a legally wedded husband or wife. However, due to recent legislation, same-sex spouses of U.S. citizens and Lawful Permanent Residents, along with their minor children, are now eligible for the same immigration benefits as opposite-sex spouses.
Bear in mind that "living together" with another individual does not form the basis to apply for a marriage visa. Also, according to the US Deparment of State "common-law spouses may qualify as spouses for immigration purposes depending on the laws of the country where the common-law marriage occurs. In cases of polygamy, only the first spouse may qualify as a spouse for immigration."