Brain lesions can allow for causal links between symptoms and human neuroanatomy. However, lesions causing the same symptom often fail to overlap a single brain region, leaving the localization unclear. Resting-state functional connectivity MRI is a powerful tool for mapping human brain networks. Using resting-state functional connectivity, one can test whether lesions causing the same symptom map to a functionally connected brain network rather than a single brain region. This approach, termed “lesion network mapping,” has proven useful for mapping a wide variety of lesion-induced neurological and psychiatric symptoms to brain networks. These lesion network mapping results are reproducible across independent datasets and show promise for identifying therapeutic targets for neuromodulation. Here, we review the methodology for lesion network mapping using functional connectivity MRI.