Billy Four was an American automobile brand established in 1910 by McNabb Iron Works, located in Atlanta, Georgia. The company produced a distinctive two-seater roadster known for its appealing design and engineering features.

The Billy Four roadster was equipped with a 20-horsepower four-cylinder engine, an epicyclic gearbox, and a shaft drive system. The initial offering, referred to as Model 1, was priced at $500. Notably, there was no subsequent Model 2 produced by the company.

Despite its attractive design and specifications, the brand's production was limited, and it did not achieve significant market presence.