This Chapter presents micromachined resonator and its applications in Radio Frequency (RF) circuits. A wide range of topics and prior work related to MEMS resonators are covered to provide readers with a better understanding up to a reasonable extent. Initially, operating principles of the MEMS resonators and their properties are discussed. Primary modes of the resonators are discussed that includes flexural modes, bulk modes, shear modes and torsional modes. It then discusses three different transduction techniques like capacitive, piezoelectric and piezoresistive. Different challenges behind the manufacturing of MEMS resonators are also discussed. Finally, emerging applications of MEMS resonators, namely their use in timing, sensing and radio-frequency systems are described. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.