An antenna system includes a dielectric substrate, a ground element, and a first antenna element. The dielectric substrate has a first surface and a second surface, which are opposite to each other. The ground element is disposed on the first surface of the dielectric substrate. The first antenna element includes a first radiation element, a feeding radiation element, a second radiation element, and a shorting radiation element. The first radiation element has a feeding point, and is disposed on the second surface of the dielectric substrate. The feeding radiation element is adjacent to the first radiation element. The second radiation element is coupled to the feeding radiation element. The second radiation element is further coupled through the shorting radiation element to the ground element.