An optical module includes a housing including an internal space that has an opening in a substrate mounting surface, an element mounting surface that forms a portion of an inner surface of the internal space, and a waveguide introduction opening that is formed in a side surface intersecting the substrate mounting surface and is opened to the opening of the substrate mounting surface and communicated with the internal space, an optical element that is mounted on the element mounting surface, and an electronic element that is mounted on the element mounting surface and is connected to the optical element. When the substrate mounting surface is mounted on a circuit substrate, an optical waveguide that protrudes from a surface of the circuit substrate is introduced into the internal space through the waveguide introduction opening.