Is Workers Compensation a federal law?

Excuse me, could you clarify for me if Workers Compensation is indeed a federal law that applies uniformly across all states in the United States? I've heard conflicting information, and I'm trying to understand the true nature of this system that provides financial and medical benefits to employees who suffer work-related injuries or illnesses. Is it mandatory for all employers to offer Workers Compensation insurance, or does it vary by state regulations? I'd appreciate your insights on this matter.