| Diamantis Nikolaou Διαμαντής Νικολάου | |
| Birth Date: | c. 1790 |
| Death Date: | 19 January 1856 |
| Nationality: | Greek |
| Father: | Nikolaos Kateriniotis Olympios |
Adamantios Olympios Nikolaou (c. 1790 – January 19, 1856), better known as Captain Diamantis, was a Greek klepht and an armatolos from Pieria.
Born in Ryakia, Diamantis Nikolaou Olympian was the eldest son of the great armatolos and klepht Raideniotis (Ryakiotis) Olympios, best known as Nikolas Kateriniotis Olympios. He operated in the mountains of Vermio, Olympus and Pieria before 1821 and after the outbreak of the Revolution. The interim government and the Supreme Court because of his bravery and military skill appointed him commander of Evia and Eastern Greece. He successfully confronted the Turks in Evia and in the battle of Faucets. In 1829, as shown in the paroikoi Skopelos records (2 April 1829) he was with his family on the island of Skopelos. In July 1829 he represented Thessalomakedones fighters in the Fourth National Assembly at Argos and offers to Kapodistrias their proxy. By decision of King Otto, he was appointed senator on June 16, 1844 in the Senate body.