• Compared to human-generated online reviews, ChatGPT-generated reviews were considered less useful, less trustworthy and less authentic. • Perceived authenticity mediates the relationships between online review source (human vs ChatGPT) and online review trust and online review usefulness. • The review source effects on usefulness, trust and authenticity are robust regardless of review valence.. While artificial intelligence's (AI) promise for fake online review detection has been investigated, other questions have emerged with ChatGPT's introduction, a generative AI platform. This research provides a much-needed investigation into consumer reactions to reviews perceived to be generated by ChatGPT vs. a human. Results from three studies in TripAdvisor hotel review and Yelp restaurant review contexts revealed that consumers rate reviews as less useful, trustworthy, and authentic if they perceived ChatGPT generated them. Further, the findings were robust regardless of review valence and even when participants were informed the reviewer possessed a TripAdvisor Expert badge. These findings' theoretical and practical implications are discussed, along with limitations. [ABSTRACT FROM AUTHOR]