Romanos III Argyros (or Romanus III Argyrus) (Greek: Ρωμανός Γ΄ Αργυρός, Rōmanos III Argyros) (968 – 11 April 1034) was Byzantine emperor from 15 November 1028 until his death.

Romanos Argyros was the son of an unnamed member of the Argyros family and a great-grandson of Emperor Romanos I. His sister Maria had married Giovanni Orseolo, a Venetian lord in Dalmatia. He also had a brother, Basil Argyros. Under Basil II Romanos served as judge, and under Constantine VIII he became urban prefect of Constantinople. Romanos attracted the attention of Constantine VIII, who forced him to divorce his wife (sending her into a monastery) and to marry the emperor's daughter Zoe. The marriage took place on November 12, 1028, and three days later Constantine VIII died, leaving Romanos III as emperor.

The new emperor showed great eagerness to make his mark as a ruler, but was mostly unfortunate in his enterprises. He spent large sums upon new buildings and in endowing the monks, and in his endeavour to relieve the pressure of taxation disorganized the finances of the state. Idealizing Marcus Aurelius, Romanos aspired to be a new "philosopher king", and similarly desired to imitate the military prowess of Trajan.