Over the past years, substantial advances have deepened our understanding of the cellular and molecular drivers of brain energy metabolism. Enabled by transformative technologies offering cellular-level resolution, these insights have revealed a highly regulated and dynamic metabolic interplay among brain cell types, particularly between neurons and astrocytes. In this Review, we shed light on the intricate ways in which neurons and astrocytes operate as a metabolically coupled unit, optimized to sustain the energetic demands of neurotransmission while ensuring neuroprotection. We highlight intercellular cooperation as a key determinant of brain function and provide examples of how disruption of the neuron–astrocyte metabolic unit contributes to numerous diseases of the nervous system, underscoring the critical importance of continued fundamental research to dissect the regulatory principles and vulnerabilities of this intercellular metabolic axis and identify potential therapeutic targets.