The biosynthetic machinery of the first fungal ribosomallysynthesized and post‐translationally modifiedpeptide (RiPP) ustiloxinB was elucidated through a series of gene inactivation and heterologous expression studies. The results confirmed an essential requirement for novel oxidases possessing the DUF3328 motif for macrocyclization, and highly unique side‐chain modifications by three oxidases (UstCF1F2)