Ardo Smaragdus (died March 843 AD) was a hagiographer. He entered the monastery of Aniane in Hérault as a boy, probably as an oblate, and was brought up by Saint Benedict of Aniane. He was ordained a priest and made head of the monastery school. In 794, he accompanied Benedict to the Council of Frankfurt. and in 814, he replaced Benedict as abbot after the latter joined the imperial court at Aix-la-Chapelle.