Differentiation arrest and dependence on oxidative metabolism are features shared among genetically diverse acute myeloid leukemias (AMLs). A phenotypic CRISPR-CRISPR-associated protein 9 screen in AML identified dependence on phosphoseryl-transfer RNA kinase (PSTK), an atypical kinase required for the biosynthesis of all selenoproteins. In vivo, PSTK inhibition (PSTKi) impaired AML cell growth and leukemic stem cell self-renewal. Notably, timed pharmacologic PSTKi effectively targeted chemotherapy-resistant AML in murine and patient-derived xenograft models, showing selectivity for malignant cells over normal hematopoietic cells. Mechanistically, PSTKi-induced reactive oxygen species (ROS) triggering mitochondrial DNA release into the cytosol and activated cyclic GMP-AMP Synthase-Stimulator of interferon genes (cGAS-STING). This activation, in turn, disrupted iron metabolism, augmenting ROS generation, and amplifying ferroptosis. Together, these findings reveal a self-reinforcing PSTK-cGAS-STING-ROS loop, culminating in an oxidative crisis and ferroptotic cell death of leukemic stem cells. These data highlight the potential for augmenting standard cancer chemotherapies using timed metabolic intervention to eliminate chemotherapy-persisting cells and thereby impede disease relapse. © 2025 American Society of Hematology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.