This application provides an antenna apparatus and a terminal device. The antenna apparatus includes an antenna patch, a
feed line, a
capacitor, and a
ground line. One end of the
feed line is connected to the antenna patch. The other end of the
feed line is connected to the
capacitor in series. One end of the
ground line is connected to the antenna patch. The other end of the
ground line is configured to connect to the
ground plane. The antenna patch and the
ground plane remain spaced apart. The antenna patch, the feed line, and the ground line work together to excite operation
modes corresponding to three resonances, to increase a low-frequency bandwidth of the antenna apparatus. In this application, the antenna patch, the feed line, the
capacitor, and the ground line may work together, so that the antenna apparatus and the
ground plane together form three
resonance circuits. In other words, the operation
modes corresponding to three resonances are excited. As a result, the antenna apparatus achieves a relatively large low-frequency bandwidth that can cover a
frequency band of 698 MHz to 1500 MHz. In addition, while good
radiation performance is ensured, a structure of the antenna apparatus is simplified and a size of the antenna apparatus is decreased, so that the antenna apparatus is simpler and more compact, and meets a requirement for a miniaturized design.