Kenworth is an American manufacturer of medium and heavy-duty Class 8 trucks based in Kirkland, Washington, United States, a suburb of Seattle, Washington . It is a subsidiary of PACCAR, and is also a former manufacturer of transit buses and school buses.

Kenworth began its history in Portland, Oregon. In 1912, the company was founded by brothers George T. and Louis Gerlinger, Jr. as a car and truck dealership known as Gerlinger Motor Car Works. In 1914, they decided to build their own truck with a more powerful inline six-cylinder engine. This was the first ever put into a commercial truck. The Gersix, as it was known, unveiled in 1915, was framed in structural steel, which along with its power, made the truck ideal for the rugged Northwest, where it was used for logging.

In 1916 the Gerlinger Motor Car Company moved to Tacoma, Washington. Seattle businessman Edgar K. Worthington was managing his mother's commercial building, where Gerlinger became a tenant, and became intrigued by the Gerlinger company. Worthington's tenant was doing quite well, or so it seemed, and the Gersix became a popular fixture in the Northwest. In 1917 Worthington and his business partner Captain Frederick Kent bought the Gerlinger business, renaming it the Gersix Motor Co.