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 has 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.
Smaragdus wrote the life of St. Benedict of Aniane in 822, one of the most reliable hagiological productions of that period. He himself was honored as a saint at his monastery after his death.