This article discusses the current status of X-ray sources (tubes and power supplies) used in handheld X-ray fluorescence instruments. It outlines the basics of the tube and high-voltage power supply (HVPS) design and the functionality of X-ray sources designed specifically for handheld X-ray fluorescence (XRF). Further, the testing methodologies of the tubes and power supplies are discussed. Finally, the selection criteria for the X-ray source for common applications are presented.