Elementary Number Theory offers a fresh and engaging exploration of one of mathematics' most timeless and beautiful fields. Designed for master's students and advanced undergraduates, it blends classical insights with modern perspectives to reveal the elegance and power of numbers-from ancient theorems to real-world applications. Drawing on over decades of classroom experience, the author presents a carefully sequenced development of topics, beginning with divisibility and congruences, moving through quadratic reciprocity, and culminating in contemporary themes such as cryptography. The text strikes a rare balance between rigor and accessibility, ensuring that readers not only master techniques but also develop a deep appreciation for the subject's underlying ideas. Notably, the book introduces abstract structures earlier than most standard texts, helping students build a strong conceptual framework from the outset. It also incorporates less commonly covered but highly valuable tools, such as p-adic valuations and matrix methods for continued fractions, which open doors to richer problem-solving strategies. Richly supported by classroom-tested exercises, worked examples, and intuitive explanations, Elementary Number Theory is as effective for guided learning in the classroom as it is for self- study. Whether you are preparing for advanced research or simply seeking to experience the intellectual beauty of number theory, this book offers a rewarding journey through one of mathematics' most fascinating landscapes.