Oryzamutaic acid A, a novel yellow pigment, was isolated from the endosperm (polished rice) of an Oryza sativa mutant. The structure and absolute configuration of oryzamutaic acid A were elucidated on the basis of spectroscopic analysis, single-crystal X-ray diffraction analysis, and biogenetic reason. Oryzamutaic acid A might be biogenetically derived from four L-amino acids because it contains three amino acid groups and one amine group.