This book presents the general theory of categorical closure operators to- gether with a number of examples, mostly drawn from topology and alge- bra, which illustrate the general concepts in several concrete situations. It is aimed mainly at researchers and graduate students in the area of cate- gorical topology, and to those interested in categorical methods applied to the most common concrete categories. Categorical Closure Operators is self-contained and can be considered as a graduate level textbook for topics courses in algebra, topology or category theory. The reader is expected to...