This is another edition of a popular introductory book to graph theory. Like the previous versions, it is aimed at mathematics students and it treats the topic with rigorous but easy to read pace. The topics covered include basic notions such as trees, cycles and connectivity, and it gently moves to more involved issues of planarity and graph embeddings on surfaces, graph colourings, the Ramsey theory, extremal graph theory, matchings and factorizations, domination in graphs and a sample of applications of the probabilistic method. The sections that have been most thoroughly revised compared to the previous editions are those on graph colouring (including list colouring and modern related trends in the chromatic theory of graphs), Ramsey theory (with generalized and rainbow Ramsey theorems) and domination theory (introducing independent domination and other variants of this concept). All these revisions follow the most recent development in their fields.