<ul data-eligibleForWebStory="false">In non-truthful auctions like first-price and all-pay auctions, independent strategic behaviors of bidders can lead to undesirable outcomes.Coordinating bidders by having a mediator recommend correlated bidding strategies can improve auction systems.Learning Bayes correlated equilibria in non-truthful auctions requires understanding bidders' private valuations, which may not always be available.The sample complexity of learning Bayes correlated equilibria in auctions can be achieved with a polynomial number of samples.