Smart fluids are a class of advanced materials that exhibit dynamic changes in their flow properties in response to external excitations. These fluids are widely used across multiple engineering disciplines due to their ability to adapt and respond to varying environmental conditions. Their unique characteristics make them highly suitable for applications requiring precise control over flow behavior. Smart fluids can be broadly categorized into six main groups: ferrofluids, electrorheological fluids, magnetorheological fluids, photo-rheological fluids, electro-conjugate fluids, and shear thickening fluids. This chapter provides an overview of these smart fluids, briefly introducing these fluids and their practical implementations across various industries.