Francis Diaz was an 18th-century Spanish Dominican missionary and bishop who served in China. Born in Écija, Spain, in 1713, he joined the Dominican Order in 1730. Due to eye health issues that limited his academic pursuits, he focused his studies on moral theology. After being ordained in Manila, he traveled to China in 1738. He worked clandestinely to serve Catholic communities during a period when foreign missionary activities were prohibited by the Manchu Dynasty.