Social media has rapidly emerged as a pivotal marketing channel influencing consumer buying behaviour, especially among India’s urban youth. This research paper examines how social media marketing on platforms such as Instagram, Facebook, YouTube, and WhatsApp shape the purchase decisions of young urban consumers in industries like fashion, electronics, and fast-moving consumer goods (FMCG). Drawing on recent statistics (2023–2025), industry reports, and academic studies, the paper analyses trends in social media usage, the impact of influencer marketing, and notable brand campaigns in the Indian context. The findings indicate that social media significantly affects each stage of the consumer decision-making process—from awareness and product research to purchase and post-purchase engagement. Case studies of successful Indian social media campaigns illustrate the strategies brands use to engage youth and drive sales. The paper concludes with insights into the growing role of social media in shaping consumer preferences and recommendations for marketers to effectively harness these platforms.