This article provides a comprehensive analysis of sustainable indices (also known as ESG indices) in India and globally, examining their definition, importance, and evolution within the financial landscape. Unlike traditional market benchmarks, sustainable indices integrate environmental, social, and governance (ESG) factors to assess long-term value creation and risk mitigation. The report delves into major sustainable indices, their construction methodologies, and their impact on portfolio performance and investor perception. It also addresses critical challenges such as greenwashing, the lack of standardized ESG metrics, and data availability issues. Finally, the report explores future trends, including the growth of ESG ETFs, the increasing influence of AI and big data analytics in ESG investing, and the continuous evolution of regulatory frameworks to promote responsible investment practices..