Green infrastructure (GI) is increasingly recognized as a pivotal strategy in sustainable urban development, offering multifaceted ecosystem services that address pressing environmental challenges including climate change, urban heat island effects, stormwater management, and biodiversity loss. This article presents a comprehensive analysis of GI frameworks, comparative assessments of dominant green technologies, and quantitative sustainability outcomes derived from empirical data across twelve global cities. Results indicate that integrated GI systems achieve up to 60% reduction in urban heat island intensity, 62% decrease in stormwater runoff, and 43% reduction in greenhouse gas emissions per hectare annually. These findings underscore the critical importance of embedding GI as a core pillar within urban planning policy and sustainable city development strategies, aligned with global Sustainable Development Goals (SDGs).