John Alexander Thain (born May 26, 1955) was the last chairman and chief executive officer of Merrill Lynch before its distressed merger with Bank of America. Thain was designated to become president of global banking, securities, and wealth management at the newly combined company, but he resigned on January 22, 2009. Ken Lewis, CEO of Bank of America, forced John Thain to resign after losses at Merrill Lynch proved to be far larger than the due diligence team at Bank of America had estimated.

On December 8, 2008, Thain gave up on pursuing a controversial bonus of $10 million from the compensation committee at Merrill Lynch on that company's last day as an independent company.

On January 22, 2009, it was revealed that, in early 2008, Thain spent $1.22 million in corporate funds to renovate two conference rooms, a reception area, and his office - including $131,000 for area rugs, a $68,000 antique credenza, guest chairs costing $87,000, a $35,000 commode, and a $1,400 wastebasket. Thain subsequently apologized for the obvious lapse in judgment, and reimbursed the company in full for the costs of the renovation.