This Is How You Lose the Time War is a 2019 science fiction fantasy LGBT epistolary novel by Amal El-Mohtar and Max Gladstone. It follows two enemy agents who travel back and forth through time to alter history on behalf of their warring empires, whose timelines are mutually exclusive. It was first published by Simon & Schuster. It won the BSFA Award for Best Shorter Fiction, the 2019 Nebula Award for Best Novella, the 2020 Locus Award for Best Novella, the 2020 Hugo Award for Best Novella, and the 2020 Ignyte Award for Best Novella.