This chapter explores the characteristics, success factors, and contributions of vibrant streets to sustainable development. Vibrant streets are dynamic, energetic urban spaces where pedestrians, cyclists, and vehicles coexist, supporting both movement and place functions. These streets are essential for fostering community interaction, economic vitality, and environmental sustainability. The chapter identifies key characteristics of vibrant streets, including active use, diverse functions, and successful businesses, which contribute to their lively atmosphere. Successful vibrant streets balance three functions: movement (efficient transportation of people and goods), place (providing areas for social interaction), and environmental functions (climate adaptation and water management). Key factors contributing to their success include walkability, well-designed public spaces, and mixed land use, which enhance both pedestrian volumes and the quality of place-based activities. The chapter also highlights broader contributions of vibrant streets to sustainable urban development. By promoting walking, cycling, and public transport, vibrant streets reduce greenhouse gas emissions, improve public health, and foster social inclusion. Furthermore, they enhance the urban environment by integrating green spaces and promoting resource efficiency. Ultimately, vibrant streets are vital components of sustainable urbanism, supporting the goals of accessibility, environmental stewardship, and social equity, all while enhancing the quality of urban life and promoting long-term resilience.