Mario Onnis was born in Sardegna. In Macerata he attended a course of illustration with Francesca Ghermandi and, after that, courses with Carll Cneut, Roberto Innocenti and Pia Valentinis. After the Master Ars in Fabula he published “Oliver Twist” (2013) and, thereafter, “Moony Goes on Holiday” (2016) for the publishing house Helbling Languages. He was selected for the Illustrators Exhibition at the Bologna Children's Book Fair in 2014. In 2016 he illustrated “Guarda le stelle”, written by Gabriele Clima and edited by Fatatrac. The following year, collaborating with the spanish publishing house Thule, he published “La cometa perdida”.