This document describes a single-layer air waveguide antenna integrated on a circuit board. The waveguide guides electromagnetic energy through channels filled with air. It is formed from a single layer of material, such as a sheet of metal, metal-coated plastic, or other material with conductive surfaces that is attached to a circuit board. A portion of a surface of the circuit board is configured as a floor of the channels filled with air. This floor is an electrical interface between the circuit board and the channels filled with air. The single layer of material is positioned atop this electrical interface to define walls and a ceiling of the channels filled with air. The single layer of material can be secured to the circuit board in various ways. The cost of integrating an air waveguide antenna on to a circuit board this way may be less expensive than other waveguide-manufacturing techniques.