We are very happy to hand over this text book of S.Y.B.Sc. PHY-201-MJ: Mathematical Physics-I to S.Y.B.Sc. students. This book has been presented to you according to the revised syllabus of Savitribai Phule Pune University implemented from June 2025. An attempt is made to give more emphasis on essential modern concepts in physics. The concepts are illustrated and elaborated with necessary examples. Sufficient exercise is given at the end of each of each topic for the practice of the students. We hope that the book will fulfil the expectations of the students and teachers. We hope that this book will cater the exact requirements. We are thankful to our vibrant publisher Shri Rangrao Patil and all staff of Prasant Publications for their efforts and keen interest in publishing this book in a very limited span of time. Any comment, criticism and suggestions from the readers for improving the book will be highly appreciated.