He was born in Livorno, and trained under Guglielmo Micheli, along with Gino Romiti, Llewelyn Lloyd, Amedeo Modigliani, and Aristide Sommati.
He was a member of the Gruppo Labronico of painters that met in the Caffè Bardi.
He differed from the Macchiaioli schools who had portrayed landscapes and scenery in naturalistic light; his themes were intimate and centered on people: often portraits, but could be iconic scenes of mothers and children or just toddlers.
[1] A retrospective was held at the Pinacoteca Carlo Servolini of Collesalvetti in 2010, titled Manlio Martinelli 1884-1974 Un amico di Modigliani alla Scuola di Guglielmo Micheli, curated by Francesca Cagianelli.
This article about an Italian painter born in the 19th century is a stub.