Cyclomatic Complexity (CC) is a code metric that measures the number of independent execution paths through a method by counting branching constructs like if, while, and for statements. Introduced by Thomas McCabe in 1976, CC helps determine the minimum number of test cases needed and serves as a practical indicator of code maintainability. The guide covers CC calculation in C#, recommended thresholds (McCabe's limit of 10, Microsoft's CA1502 flag at 25), and refactoring strategies to reduce per-method complexity by distributing logic across smaller, focused methods.