Emiliano Mercado del Toro (born August 21, 1891) is a supercentenarian resident of Puerto Rico, probably its oldest inhabitant after the death of Ramona Trinidad Iglesias-Jordan. He first came to the attention of longevity researchers in 2001, when a story ran about a 110-year-old veteran in a parade in Puerto Rico. Since that time, researchers have been trying to track him down, but only after the death of Fred H. Hale, Sr. did someone finally start sending in documents. Following Fred's passing Emiliano apparently became the oldest man in the world, with documents supplied so far including a birth certificate, baptismal certificate, 1910 census record, and veterans ID card. By January 2005 Guinness had accepted Emiliano as the "oldest living man whose age could be fully authenticated."

In addition, as a veteran of World War I, he appears to have broken the record for longest-lived veteran of any military force that was set by Antonio Todde, although Todde retains the distinction of oldest combat veteran, since Emiliano was still in training camp when the Nov 11 1918 armistice was declared.