The Robert C. Byrd Mine Safety Protection Act of 2026 strengthens federal mine safety enforcement and worker protections by significantly increasing civil penalties for violations, with fines up to $220,000 for high-risk violations like improper ventilation and doubled penalties for operators with a history of violations. The bill expands the Secretary of Labor's investigative authority to issue subpoenas and allows miners to report safety concerns confidentially to investigators, while also establishing strong protections against employer retaliation with remedies including back pay and attorney's fees. To ensure compliance, the legislation creates a powerful enforcement mechanism whereby operators who fail to pay penalties within 180 days face mandatory mine shutdowns until payment is made or a payment plan is established, with interest accruing immediately on disputed citations. The bill requires underground coal mine operators to brief workers on hazards and safety violations before each shift within 30 days and directs the Labor Department to issue regulations within 180 days. Additional provisions enhance mine rescue training, expand the Mine Safety and Health Administration's staffing capabilities through a 5-year succession plan, and clarify that all amendments apply to the Federal Mine Safety and Health Act of 1977.