An Introduction to Electromagnetic Theory is designed as a concise introduction to electromagnetic field theory emphasizing the physical foundations of the subject. It is aimed at an undergraduate readership, primarily physics students. As such, it covers much material from the standard university syllabus. Additionally, however, it develops a number of themes in greater detail, so as to cover a number of non-standard topics that provide a fuller understanding of the subject, by filling in gaps sometimes encountered in other texts. A key aspect to the book is the macroscopic approach to the subject from the outset. Most readers will have some familiarity with the standard mathematics employed, but a review chapter is provided at the beginning to help give some guidance on these topics as they are used throughout the book.