Resonant microelectromechanical systems (MEMS) are characterized by sub-millimeter-sized components that are able to oscillate. Depending on the actuation method, these resonant MEMS are implemented, e.g., as electrostatic, electrothermal, magnetostatic or piezoelectric devices. The distinct characteristics of these devices such as a wide frequency range, favorable signal-to-noise ratios, reliability, low power consumption and small size make them useful for a variety of applications ranging from sensors to timing devices. The book covers the principles, modeling and implementation as well as applications of resonant MEMS from a unifi ed viewpoint. It starts out with the fundamental equations and phenomena that govern the behavior of resonant MEMS and then gives a detailed overview of their implementation in capacitive, piezoelectric, thermal and organic devices, complemented by chapters addressing the packaging of the devices and their stability. The last part of the book is devoted to the cutting-edge applications of resonant MEMS such as inertial, chemical and biosensors, fluid properties sensors, and energy harvesting systems.