Ottavio Semini (c. 1530-1604) was an Italian painter of the late-Renaissance.
He was born and trained in Genoa and died in Milan. He was the son and pupil of Antonio Semini, and was influenced by Perino del Vaga. Aided his brother Andrea in many works, but was obliged to leave Genoa on account of a homicide, and afterwards led a dissipated life in Milan. He helped paint for the chapel of San Girolamo in St. Angelo in Milan. One of his pupils was Paolo Camillo Landriani.