It gives me immense pleasure in introducing my first book named as "High-Pressure ElectroChemistry and Applications" based on my PhD works. This book explained on newly self-developed high-pressure instruments combined with available Electro- analyzers. This deals with electrochemical aspects of the development and applications of HP-EQCM. The discussion of these aspects develops through the fundamentals of electrochemical experiments (CV, EQCM) separately or simultaneously in HP-system via the interaction of electrochemical behaviors to finally include the interfacing of the high-pressure chemistry world. The final focus is investigated on the construction and applications by HP- EQCM from 14.7 ( 1 atm) to 25000 PSi. I worked consistently for almost four years to accomplish this work under the proper guidance of my respective PhD supervisor. I hope that this work would further enhance the electrochemistry, especially in bringing new entrants into the high-pressure electrochemistry fields and help scientists to pick-up/forward and develop their own field of specialization. There are bound to be a few lapses in the work of this magnitude