The large yellow M used in McDonald's restaurant design is known as the Golden Arches.
The arches originated as architectural features on McDonald's early restaurant buildings. The original restaurants used two separate yellow arches visible from the roadside, helping motorists recognize the locations. The design drew attention to the building before the modern logo became standardized.
In 1962, the arches were combined into the recognizable M-shaped corporate symbol. The logo transformed an architectural feature into a compact brand mark that could appear on signs, packaging, uniforms, and advertising.
The Golden Arches are sometimes described simply as the McDonald's logo, but the phrase also refers to the architectural elements that inspired it. That distinction explains why the term appears in both restaurant-design and graphic-branding histories.