Artificial intelligence (AI) has revolutionized digital advertising by enabling real-time targeting, automated segmentation, predictive engagement, and personalized messaging. However, algorithmic processes frequently reproduce or amplify social, cultural, racial, linguistic, and political biases—especially visible across international markets. This research examines forms and causes of algorithmic bias in global advertising systems, analyzing platforms such as Google Ads, Meta Ads, TikTok, and programmatic DSP networks. Using interviews with industry experts, content sampling across 14 countries, and documentation reviews, the study finds that algorithmic bias emerges through data asymmetry, cultural stereotypes in training sets, unequal digital access, language prioritization, and political filtering. A cross-cultural bias mitigation framework is proposed to support ethical global advertising.