The Danube holds a strategic position and is a key region for economic cooperation, transportation, and energy security. In the context of the global energy transition and the European Union's climate neutrality objectives, sustainable energy is becoming central to the future of the Danube region. This paper presents an empirical analysis of renewable energy development in the Danube region. The study is based on Eurostat data covering the period 2013–2023 and examines key indicators such as the share of renewable energy in the energy mix, installed capacity, and the evolution of major renewable energy sources. Hydropower offers important advantages, including relatively stable energy production and low carbon emissions, but its dependence on hydrological conditions and impacts on aquatic ecosystems are major limitations. Beyond hydropower, solar and wind energy are gaining increasing importance in the Danube region. Over the last decade, investment in these renewable sources has increased significantly, helping to diversify the energy mix and reduce dependence on hydropower. Biomass is also an important component of sustainable energy in the Danube region, especially in rural areas. The use of agricultural residues, forestry waste, and dedicated biomass contributes to the production of heat and electricity while supporting the local economy. However, the development of sustainable energy in the Danube region faces many challenges. Climate change is having a direct impact on the hydrological regime of the Danube, affecting the flow of the river and, consequently, hydropower production. This study outlines the region's potential to support the European energy transition and regional green energy cooperation. At the same time, the paper aims to highlight existing opportunities and good practices at the regional and European levels, emphasizing cross-border cooperation, EU policies, and the role of technological innovation.