Fiancé visas, also known as K-1 visas in the United States, are a type of non-immigrant visa that allows a foreign national engaged to a U.S. citizen to enter the United States for the purpose of getting married. Once the marriage takes place, the foreign fiancé can apply for adjustment of status to become a lawful permanent resident (green card holder). Here are the key aspects of fiancé visas:

Eligibility Requirements:

1. Engagement: The petitioner (U.S. citizen) and the beneficiary (foreign fiancé) must have a genuine, bona fide intention to marry. They must have met in person at least once within the two years preceding the visa petition filing, with limited exceptions.

2. Eligible Relationship: Only U.S. citizens can petition for K-1 visas. Legal permanent residents (green card holders) cannot apply for their fiancés.

Application Process:

1. File Petition: The U.S. citizen petitioner initiates the process by filing Form I-129F, Petition for Alien Fiancé(e), with U.S. Citizenship and Immigration Services (USCIS). This petition must include supporting documents, evidence of the relationship, and a filing fee.

2. Approval: Once USCIS approves the petition, it is sent to the U.S. Embassy or Consulate in the beneficiary's home country, where the fiancé visa application process continues.

3. Visa Application: The beneficiary applies for the K-1 visa at the U.S. Embassy or Consulate, attends an interview, and undergoes a medical examination.

4. Background Checks: Both the petitioner and beneficiary are subject to background checks, security clearances, and medical examinations as part of the visa application process.

K-1 Visa Issuance:

1. Approval: If the consular officer approves the visa application, the beneficiary will be issued a K-1 visa.

2. Entry: The beneficiary can travel to the United States with the K-1 visa within the validity period (usually 6 months) to marry the petitioner.

3. Marriage: Once in the United States, the beneficiary and petitioner must marry within 90 days of the beneficiary's entry. Failure to marry within this timeframe can result in the beneficiary's legal status becoming invalid.

Adjustment of Status:

1. Application for Adjustment of Status: After marriage, the K-1 visa holder must apply for adjustment of status to become a lawful permanent resident (green card holder) using Form I-485.

2. Conditional Green Card: In many cases, the initial green card granted through the adjustment of status process is conditional and valid for two years. The couple must jointly petition to remove the conditions during the 90-day window before the green card expires.

Rights and Responsibilities:

1. Work Authorization: K-1 visa holders are eligible to apply for work authorization in the United States.

2. Travel: K-1 visa holders can travel outside the United States, but they must be cautious about re-entry requirements.

3. Legal Obligations: Both the petitioner and beneficiary are legally obligated to follow the terms and conditions of the K-1 visa, including getting married within the 90-day period.

It's essential to consult with an immigration attorney or expert to navigate the fiancé visa process successfully, as it involves complex immigration laws and procedures. Additionally, it's important to plan carefully for the wedding and the adjustment of status process to ensure a smooth transition to lawful permanent residency.