This dissertation examines the effectiveness of online advertising on customer purchase intentions, specifically focusing on Morrison's, a major UK supermarket chain. The study investigates the impact of online advertising strategies on consumer behavior within the competitive retail sector. It explores the rationale behind online advertising's significance, considering the decline of traditional advertising methods and the increasing influence of the internet and social media. The research employs a mixed-methods approach, including primary and secondary data collection, utilizing both qualitative and quantitative analysis techniques like thematic analysis and SPSS. Findings suggest that online advertising significantly influences customer purchase intentions by providing valuable product information, attracting a broader audience, and enhancing brand image, ultimately contributing to increased business volume and customer retention. The research also addresses limitations, ethical considerations, and provides recommendations for Morrison's online advertising strategies to maintain a competitive edge in the market.