In most cases, yes, a job offer is required to apply for a U.S. work visa. For popular categories such as H-1B, H-2B, and L-1, a U.S. employer must file a petition with USCIS before you can apply. The employer essentially sponsors your visa, making the job offer a crucial requirement. Certain exceptions exist, such as the E-2 investor visa, which is based on personal investment rather than employment. However, even in treaty-based categories like E-1 or TN, you must demonstrate a pre-arranged employment opportunity in the U.S. to qualify successfully.