This comprehensive treatise presents an exhaustive, rigorous analysis of Benoit Mandelbrot's revolutionary contributions to mathematics, physics, computer science, economics, and our fundamental understanding of complex natural phenomena through the paradigm-shifting lens of fractal geometry. Benoit B. Mandelbrot (1924-2010), a Polish-French-American mathematician of extraordinary interdisciplinary breadth and iconoclastic vision, fundamentally transformed humanity's understanding of irregularity, roughness, complexity, and disorder in nature by introducing, developing, and popularizing fractal geometry—a radical new branch of mathematics that describes self-similar patterns recurring at different scales, characterized by non-integer dimensions that lie between the familiar integer dimensions of classical Euclidean geometry. This extensive scholarly investigation examines Mandelbrot's profound insights into the geometric structure and mathematical characterization of natural objects and phenomena including coastlines and national borders, mountain ranges and terrain surfaces, clouds and atmospheric turbulence, trees and botanical branching patterns, blood vessels and bronchial airways, river networks and watershed systems, galaxy distributions and cosmic structure, market price fluctuations and economic volatility, demonstrating systematically how these seemingly chaotic, irregular, and disordered forms actually follow deep underlying mathematical principles characterized by fractional dimensions, power-law scaling, and self-similarity across vastly different spatial and temporal scales.