Atypical frontotemporal lobar degeneration with ubiquitin-positive inclusions (aFTLD-U) is neuropathologically characterized by aggregation of the FET family of proteins and clinically manifests as sporadic young-onset frontotemporal dementia. Here we describe a major risk locus on chr15q14 identified through a genome-wide association study in 59 pathologically confirmed aFTLD-U cases and 3,153 controls (lead single nucleotide polymorphism rs549846383, P = 5.85 × 10-21, odds ratio 26.