Chemical engineering is inherently multidisciplinary, integrating principles from chemistry, physics, mathematics, biology, and engineering to transform raw materials and energy into valuable products and services. Although traditionally associated with chemical processing and process design, the discipline has progressively expanded into areas including biotechnology, materials science, environmental engineering, energy systems, nanotechnology, computational science, artificial intelligence, and sustainability. This review examines the multidisciplinary foundations and evolving boundaries of chemical engineering, with particular emphasis on the interactions among chemical sciences, transport phenomena, thermodynamics, reaction engineering, process systems engineering, materials science, biological sciences, environmental engineering, and computational technologies. The review further discusses how emerging fields such as machine learning, digital twins, advanced materials, renewable energy, carbon capture, bioprocessing, and circular economy are reshaping chemical engineering research and practice. The convergence of these disciplines enables chemical engineers to address complex challenges involving energy security, climate change, resource scarcity, environmental protection, healthcare, food production, and sustainable manufacturing. By examining the historical development, disciplinary interfaces, technological convergence, and emerging research directions of chemical engineering, this review highlights the unique role of the chemical engineer as an integrator of scientific knowledge and engineering practice. The paper provides a conceptual framework for understanding chemical engineering as a continuously evolving multidisciplinary discipline and identifies opportunities for future interdisciplinary research, education, and industrial innovation.