| Giannis Diamantidis | |
| Honorific-Suffix: | MP |
| Office: | Minister for Maritime Affairs, Islands and Fisheries |
| Primeminister1: | George Papandreou |
| President1: | Karolos Papoulias |
| Term Start: | 7 September 2010 |
| Term End: | 17 June 2011 |
| Birth Date: | 1948 |
| Birth Place: | Nikaia, Greece |
| Nationality: | Greek |
| Party: | Panhellenic Socialist Movement |
| Residence: | Athens, Greece |
| Alma Mater: | National and Kapodistrian University of Athens |
| Profession: | Economist, Politician |
| Website: | www.gdiamantidis.gr |
Giannis Diamantidis (Greek, Modern (1453-);: Γιάννης Διαμαντίδης, born in 1948 in Athens, Greece) is a Greek politician of the Panhellenic Socialist Movement and the former Minister for Maritime Affairs, Islands and Fisheries of Greece.
Giannis Diamantidis was born in 1948 in Nikaia, Greece. He is the son of Dimitris Diamantidis, a former Member of Parliament, and Polyxeni Leontiadou. He studied at the Department of Economics and Political Sciences of the National and Kapodistrian University of Athens. During the Greek military junta of 1967–1974, he took part in the Law School protests of March 1973 against the regime.
Giannis Diamantidis has been continuously elected as a member of the Hellenic Parliament between 1989 (November) and 2012 for the Panhellenic Socialist Movement (PASOK) in the Piraeus B constituency. In the cabinet reshuffle of 7 September 2010, he was chosen to head the revived Ministry of Maritime Affairs, Islands and Fisheries, his first cabinet post. He held the position until 17 June 2011, when the ministry was again merged with the Ministry of Regional Development and Competitiveness to form the Ministry of Development, Competitiveness and Shipping.