Yes. The EOS Rebel T7i’s built-in pop-up flash can act as a wireless master for an off-camera 430EX III-RT, so you can trigger it without buying extra gear. This uses Canon’s optical wireless system, not the 430EX III-RT’s RT radio system.

To make it work, set the 430EX III-RT to optical slave mode and match the wireless channel to the camera’s flash settings. On the T7i, enable the built-in flash’s wireless/external flash control in the camera menu. You can also adjust flash ratios there if needed.

Important limitation: optical triggering generally requires line of sight and is less reliable outdoors or in bright light than radio triggering. If you want RT radio control instead, you’ll need a compatible radio master/transmitter on the camera, such as Canon’s ST-E3-RT or another RT-capable master.