The focus of this thesis is research on the influence of fitness influencers on consumer behavior with special emphasis on the Croatian market. In the era of digital communication, influencer marketing has become a key tool in the promotion of products and services, and fitness influencers occupy a prominent place in this dynamic. Thesis analyzes how content posted by fitness influencers via social media, such as Instagram and TikTok, shapes consumer perceptions and their purchasing decisions regarding fitness-related products and services, including supplements, exercise equipment, sportswear, and exercise programs. The research was conducted through a survey questionnaire that was distributed through social media, and the results showed that followers of fitness influencers attach great importance to the quality of the content, the influencer's authenticity and expertise, while the number of followers has a much smaller influence on their decisions. It has also been found that consumers often make purchasing decisions based on influencer recommendations, especially when they are linked to discounts and promotional codes. Despite the considerable influence of influencers, research has shown that there is no connection between the type of content that influencers publish and the perception of the quality of fitness products, which suggests that other factors are more important. Research limitations include a specific sample of respondents and sample bias, which reduces the possibility of generalizing the results. Future research should include a larger and more diverse sample and combine quantitative and qualitative methods for a deeper understanding of the influence of influencers on consumer behavior. The thesis contributes to the understanding of the role of fitness influencers in the digital environment and provides guidelines for optimizing marketing strategies in the fitness industry.