**Onesimos** was an ancient Athenian vase painter who flourished in Athens around 500–480 BC. Specializing in the red-figure technique during the Early Classical period, he focused primarily on decorating drinking cups, most often of Type B. Over two hundred vessels have been attributed to him, reflecting his prolific output and high demand in the Attic pottery workshops.)

His training appears closely tied to the master potter and painter Euphronios. Several cups painted by Onesimos bear Euphronios’s signature as potter, indicating close collaboration. Stylistic similarities and this partnership strongly suggest that Onesimos learned his craft as Euphronios’s pupil. He worked within the vibrant tradition of Attic red-figure vase painting, emphasizing dynamically posed, realistically rendered figures drawn from both mythology and scenes of everyday Athenian life.)

Among his notable works are finely detailed cups and other vessels featuring mythological subjects, such as a centauromachy on a red-figure psykter now in the Villa Giulia in Rome. His compositions often capture movement and narrative tension with elegant line work and careful attention to anatomy and drapery. While specific individual masterpieces are less frequently singled out than those of his contemporaries, the sheer volume of surviving attributions underscores his technical skill and artistic consistency.

Onesimos’s legacy extends beyond his own production. His influence is evident in the work of the slightly later Antiphon Painter, whose style closely resembles Onesimos’s, suggesting that Onesimos himself may have trained the next generation. As one of the leading cup painters of his era, he helped shape the transition from Archaic to Classical conventions in Greek vase painting, leaving a substantial body of work that continues to illuminate daily life and artistic practices in ancient Athens.