A Modern Introduction to Classical Electrodynamics is suitable for undergraduate students with some background knowledge of the subject and for graduate students, while more advanced topics make it a useful resource for PhD students and researchers. The book places much emphasis on the formal structure of the theory; beginning with Maxwell's equations in the vacuum, it emphasises the central role of gauge invariance and Special Relativity. After introductory chapters which include rederivations of elementary results of electrostatics and magnetostatics, and the multipole expansion, Special Relativity is introduced, and most of the subsequent derivations are performed using covariant formalism and gauge potentials, allowing for greater conceptual and technical clarity compared to more traditional treatments. The second part of the book covers electrodynamics in material media. This includes Maxwell's equations in material media, frequency dependent response of materials and Kramers-Kronig relations, electromagnetic waves in materials, and scattering of electromagnetic radiation. Finally, the text also includes advanced topics, such as the field-theoretical treatment of classical electrodynamics as a modern treatment of radiation reaction. These parts are meant for the advanced reader and are clearly marked, and can be skipped without loss of continuity.