The goal of this chapter is to connect optimization theory with actual practice by showcasing a wide range of real-world applications across different disciplines. Specifically, we present examples in the following Engineering areas: Industrial, Mechanical, Civil, Chemical, Electrical, Aerospace, and Computer. We also include examples specific to Data Science. The intention here is to demonstrate how both single-objective and multi-objective optimization techniques help solve complex challenges. These range from improving efficiency in traditional industrial processes, like supply chain management and plant operations, to designing advanced systems such as aerospace vehicles and integrated circuits. In Data Science, we also showcase how optimization is foundational to modern practices, covering machine learning model training, hyperparameter optimization, and generative AI.