| Theodora Giareni | |
| Birth Place: | Marousi, Athens, Greece |
| Headercolor: | lightsteelblue |
| Show-Medals: | yes |
Theodora Giareni (born 3 March 1990 in Marousi, Athens, Greece) is a Greek swimmer. At the 2012 Summer Olympics, she competed for the national team in the Women's 4 x 100 metre freestyle relay. The team finished in 16th (last) place in the heats, failing to reach the final.
She failed a doping control test was sent home from the 2016 Rio Olympic Games. In 2017 she received a 4-year ban from swimming competition.