Tatyana Polnova (Russian: Татья́на Полнова), née Zaykova (За́йкова, born 20 April 1979) is a Russian pole vaulter. Between 1998 and 2002 she competed for Turkey under the Turkish name Tuna Köstem. She is currently Fenerbahçe Athletics Club member.
Her personal best is 4.78 metres, achieved in September 2004 in Monaco.
International competitions
| Year | Competition | Venue | Position | Result | Notes |
|---|---|---|---|---|---|
Representing  Russia | |||||
| 1997 | European Junior Championships | Ljubljana, Slovenia | 8th | 3.75 m | |
Representing  Turkey | |||||
| 1998 | World Junior Championships | Annecy, France | 10th | 3.90 m | |
| European Championships | Budapest, Hungary | 24th (q) | 3.80 m | ||
| Representing Russia | |||||
| 2003 | Universiade | Daegu, South Korea | 1st | 4.70 m | |
| World Athletics Final | Monte Carlo, Monaco | 1st | 4.68 m | ||
| 2004 | World Athletics Final | Monte Carlo, Monaco | 2nd | 4.78 m | |
| 2005 | European Indoor Championships | Madrid, Spain | 5th | 4.60 m | |
| World Championships | Helsinki, Finland | 4th | 4.50 m | ||
| World Athletics Final | Monte Carlo, Monaco | 3rd | 4.50 m | ||
| 2006 | European Championships | Gothenburg, Sweden | 3rd | 4.65 m | |
| 2007 | World Championships | Osaka, Japan | 9th | 4.60 m | |
| 2009 | World Championships | Berlin, Germany | 7th | 4.40 m | |
