Prostate cancer has a low somatic mutation rate in coding regions, and our data suggest this extends to the UTRs of known prostate cancer driver genes, with the notable exception of FOXA1. The previously unrecognized FOXA1 3′-UTR mutations reported here, together with established forkhead domain mutations, implicate FOXA1 as the third most commonly mutated gene in advanced prostate cancer, after TP53 and AR. Here, AR is linked to prostate carcinoma.