James Ernest Duff is an American businessman, the self-made billionaire Co-owner of Southern Tire Mart and Duff Capital Investors (DCI), the largest privately owned business in Mississippi. Born in Columbia, Mississippi, in 1961, his father, Ernest Duff, was a lawyer and businessman who founded Southern Tire Mart in 1973.

Duff attended Utah Valley University, studying business. His career is rooted in truck tire distribution and manufacturing; he and his brother, Thomas Duff, worked at Southern Tire Mart as teenagers. His philosophy centers on operational excellence, scale, and unwavering commitment to the state of Mississippi.

• Southern Tire Mart (Co-owner): The core private asset, the nation's largest truck tire dealer and retread manufacturer. Its revenue exceeds $3.5 billion.
• Duff Capital Investors (DCI) (Co-founder & Co-owner): The holding company, the largest privately owned business in Mississippi (with $5.5 billion in revenues).
• Family Governance: He co-owns and manages the empire with his brother, Thomas Duff.
• Regional Focus: The Duff brothers are consistently the wealthiest individuals in Mississippi.

James Duff and Thomas Duff took over the struggling Southern Tire Mart from their father in 1983. They successfully managed the company until 1998, when they sold it to Tire Distribution Systems. Their strategic genius was the re-acquisition of the company in 2003 for $15 million, rebranding it as Southern Tire Mart. From a $90 million revenue base, they expanded the company aggressively, transforming it into the nation's largest truck tire dealer and retread manufacturer (with revenues exceeding $3.5 billion by 2023).

They co-founded Duff Capital Investors (DCI) as the umbrella holding company, overseeing a diversified portfolio that includes trucking, equipment rentals, and construction. His wealth is secured by the colossal, stable profitability of the truck tire and distribution market and the family's deep commitment to industrial vertical integration.

James Duff's social impact is structural, stemming from Duff Capital Investors' role as the largest privately owned business in Mississippi, providing over 16,000 jobs (6,000 in Mississippi alone) and contributing massively to the state's economic stability. His companies provide essential logistics and maintenance services for the U.S. commercial trucking industry.

His personal philanthropy supports various educational and community initiatives. His career is a testament to the profitability of disciplined industrial operations and the power of generational family collaboration in business management.

James Duff maintains the professional, pragmatic style of an industrial executive. His attire is consistently formal and high-quality, favoring tailored suits. His aesthetic reflects stability and serious authority, blending his background in hands-on operations with his corporate leadership.

Residing in Hattiesburg, Mississippi, his luxury is the immense security and financial reward derived from his multi-billion dollar fortune. His life is dedicated to industrial scale, logistical efficiency, and the long-term management of his essential truck tire and distribution empire.