This paper explores the transformative role of artificial intelligence (AI) in the evolving digital advertising landscape, specifically focusing on media investment, advertising effectiveness, and return on investment (ROI) optimization strategies. With the increasing integration of AI-driven technologies such as machine learning, predictive analytics, and automation, businesses are experiencing enhanced precision in targeting, personalization, and campaign management. Companies are achieving more efficient and effective advertising outcomes through AI’s ability to analyze vast datasets, predict consumer behavior, and optimize budget allocation. The paper reviews AI's significant impact on media investment strategies, such as programmatic buying, real-time bidding, and algorithmic content delivery, providing advertisers with the tools to streamline operations and maximize returns. It also delves into the methodologies for measuring the effectiveness of digital advertising, including traditional and AI-driven metrics like engagement and sentiment analysis, to highlight the potential for optimized advertising performance. Additionally, this paper presents case studies of successful AI-driven ROI optimization in various industries, underscoring the value of AI technologies in reducing ad spend waste and increasing conversion rates. The paper concludes by discussing future trends in AI-powered advertising, emphasizing the need for advancements in automation, predictive analytics, and AI ethics. It also suggests areas for further research, particularly regarding AI integration challenges and the long-term impacts on advertising ROI. This paper demonstrates how AI is revolutionizing digital advertising and offers a comprehensive framework for future research and development.