The disclosed computer-implemented method for automated classification of application network activity may include (1) building a lexicon dictionary that comprises lexical keywords, wherein network streams whose headers contain a given lexical keyword represent communications of an activity type that is associated with the given lexical keyword in the lexicon dictionary, (2) identifying, at a network vantage point, a network stream that represents a communication between an application and a server, (3) extracting, through a lexical analysis that utilizes the lexicon dictionary, a set of keywords from one or more header fields of the network stream, and (4) classifying the network stream based on activity types associated with each keyword in the set of keywords that were extracted from the header fields of the network stream. Various other methods, systems, and computer-readable media are also disclosed.