In a situation where a US citizen will be getting married to a foreign national in the US, a K-1 Visa (a/k/a a "Fiance Visa") is issued to the non-citizen fiance. It is a single entry non-immigrant visa that is obtained after the non-citizen fiance is interviewed at the US Consulate in their country of residence (this visa cannot be obtained inside the US). When the visa is issued, the non-citizen fiance has 6 months to use it to enter the US. Upon entry, it converts to a 90 day stay during which time they may get married and file for an "Adjustment of Status" in order to become a Permanent Resident of the US (i.e. get their green card). After this filing, they may reside in the US beyond the 90 day limit while their application is being processed.Note: You should be aware that both you and your fiance must in fact be free to marry; this means that you must have never been married before or any previous marriages have ended through divorce or death. You must also have met with your fiiance in person within the last 2 years prior to beginning the visa process; this requirement can only be waived in very rare circumstances.