The author thanks the participants at the Financial Intermediation Research Society Conference (2023), the Cambridge Centre for Alternative Finance Annual Conference (2023), the Northern Finance Association Annual Meeting (2023), the Financial Management Association Annual Meeting (2023), the Southern Finance Association Annual Meeting (2023), and the University of South Carolina (2022), as well as Constantin Charles, Taha Choukhmane, Donghwa Shin, Shumiao Ouyang, Raghavendra Rau, Christopher Barnes, John Hackney, Lisa Kramer, Ahmed Guecioueur, Allen Berger, Da Ke, Matthew Souther, Hugh Kim, Matthew Hood, Lindsey Woodworth, Philip Brookins, and Chao Jiang, for helpful comments and Frank Gonzalez for excellent research support. A previous version of this paper was circulated under the title “Insufficient Sleep and Intra-Day Financial Decision-Making: Evidence from Online Lending.” Any errors are the author’s own.