According to Tacitus, Galba developed a discourse about the optimus princeps when he adopted Piso on January 69, five days before both were killed at Otho's instigation. Although chosen by senators, Galba is never described as an optimus princeps in biographical and historical sources from the end of the first/beginning of the second century. This emperor of "transition" appears to be an ambiguous and controversial figure, which could be used at the beginning of the antonine dynasty to elaborate political reflections regarding the virtues of the good emperor. To better understand Galba’s figure (especially in Tacitus’ History and Plutarch’s Life), and apprehend the main issues involved, I firstly analyse how Galba’s memory was constructed under the Flavians and the first Antonines. Secondly, I study the way in which Piso’s adoption as an imperial heir was used to create a pattern of optimus princeps, which is very different from the model drawn by Pliny the Younger in front of the Senate on 1 September, 100.