Social media is an online communications medium dedicated to community-based input, interaction, and content-sharing. Websites and applications dedicated to forums, social networking, social bookmarking, etc., have proliferated, making social media an integral part of modern life. In the business landscape, social media has transformed traditional marketing paradigms, offering an interactive two-way channel to market products, promote brands, connect to current customers, and foster new business. This research explores the impact of social media marketing on consumer buying behaviour, specifically targeting the youth demographic in urban areas like Mumbai, India. The empirical data was gathered through a quantitative research approach utilizing structured questionnaires distributed to 233 respondents. The theoretical framework rests on the literature of the consumer decision-making process, incorporating psychological, personal, situational, social, and cultural factors. The findings reveal that 100% of the sampled youth utilize social media platforms, with Facebook and WhatsApp being predominant. Social media significantly assists in the information search and alternative evaluation stages of the buyer decision process. While it strongly influences buying decisions and serves as a vital tool for purchase validation and acquiring product information, a degree of mistrust regarding social media advertisements persists. The study concludes that the transparency and accessibility of user-generated content on social media have empowered consumers, making it an indispensable element of contemporary marketing strategies.