This book describes fully-integrated power management circuits for thermoelectric energy harvesting. Readers will learn about the applications, system design fundamentals, designs of building blocks, maximum power point tracking techniques, and design of battery chargers. The book covers the following key topics: 1) minimizing the cost of a thermoelectric generator (TEG) by considering the maximum open circuit voltage of TEG and the dependence of the power conversion efficiency of the converter on the input voltage, 2) controlling the input voltage of the converter system to ensure it remains higher than the minimum operating voltage, 3) designing a charge pump operating in the sub-threshold region, considering factors such as clock frequency, stage capacitor size, rectifying device size, and the number of stages, 4) implementing maximum power point tracking techniques with a small circuit area, and 5) designing a fully integrated battery charger. Readers will gain a comprehensive understanding of these concepts and their practical applications.