This book explores wireless power and data transfer (WPDT) systems, covering applications from nanowatt RFID to kilowatt electric vehicles, with a focus on efficiency and robustness. It reviews inductive and far-field coupling, coupling coefficients, multi-coil configurations, and key circuit components like power amplifiers and rectifiers. Wireless energy management ICs are discussed, including passive/active rectifiers, resonant regulating rectifiers, adaptive converters, and resonant-mode receivers. Data telemetry methods—downlink, uplink, and bidirectional—are examined alongside modulation schemes, design trade-offs, and integration with power delivery. System-level strategies include secure energy backup for authentication tags, energy reuse in medical implants, and adaptive power systems for deep brain stimulation, emphasizing efficiency, reliability, and application-specific optimization.