The reliability and continuity of transportation systems depend not only on the quality of the road superstructure but also on the effectiveness of the hydraulic structures supporting the infrastructure. Highway and railway systems not only provide physical connectivity but also directly affect the sustainability of trade, transportation safety, and quality of life. The functionality of drainage systems is crucial for ensuring the longevity and safety of this infrastructure. In this regard, culverts stand out as indispensable structures in transportation engineering. Culverts ensure that surface and underground water is removed without damaging the road structure, reducing flood risks and ensuring the continuity of the infrastructure. Inadequate or poorly designed culverts can lead to deterioration, displacement, erosion, and serious safety risks in road surfaces. Culverts can be constructed in different types, such as pipe culverts, box culverts, and arch culverts, using materials like concrete, steel, stone, or brick. During the design process, not only hydraulic capacities but also geotechnical conditions, climatic data, ease of maintenance, economic sustainability, and environmental impacts must be taken into account. In recent years, sudden rainfall caused by climate change and the increased risk of flooding have made it necessary to address culverts with more resilient and flexible design approaches. In this context, advanced hydraulic modeling methods, innovative construction materials, and ecologically focused engineering solutions have gained importance. This book chapter details the structural characteristics, functions, design criteria, application areas, and contemporary engineering approaches of culverts. Evaluations based on examples from Turkey and around the world reveal that culverts are critical not only for infrastructure safety but also for sustainable transportation systems and environmental adaptation.