As an immigrant on a work visa, can I legally start an LLC or business in the US?

Owning a US LLC is generally allowed regardless of immigration status, since passive ownership is not the same as employment. The catch is that actively working in and being paid by your own company can violate visa terms. H-1B holders, for example, are tied to a sponsoring employer and generally cannot draw a salary from a side business without separate authorization. F-1 students face strict work limits too. You can typically be an owner and investor, but running day-to-day operations or paying yourself may require the right visa or a green card. An EIN and business bank account do not require citizenship. Talk to an immigration attorney before actively operating, because the penalties affect your status, not just your taxes.