The 2005 İstanbul Cup was a tennis tournament played on outdoor clay courts. It was the first edition of the İstanbul Cup, and was part of the WTA Tier III tournaments of the 2005 WTA Tour. It was held in Istanbul from 16 through 21 May 2005.
| Event | W | F | SF | QF | Round of 16 | Round of 32 | width=85 | Q3 | width=85 | Q2 | width=85 | Q1 |
| Singles | 120 | 185 | 55 | 30 | 26 | 1 | 3.75 | 2.25 | 1 | |||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubles | 1 |
| Event | W | F | SF | QF | Round of 16 | Round of 32 | width=85 | Q3 | width=85 | Q2 | width=85 | Q1 |
| Singles | $30,500 | $16,450 | $8,840 | $4,745 | $2,550 | $1,370 | $735 | $395 | $215 | |||
| Doubles * | $9,150 | $4,900 | $2,625 | $1,410 | $760 |
The following players received wildcards into the singles main draw:
The following players received entry from the qualifying draw:
The following players received entry as lucky losers:
| Country | Player | Country | Player | Rank | Seed | |
|---|---|---|---|---|---|---|
 United States | Lisa Raymond |  Australia | Rennae Stubbs | 14 | 1 | |
| United States | Jill Craybas | United States | Jennifer Russell | 115 | 2 | |
| Emmanuelle Gagliardi |  Turkey | İpek Şenoğlu | 125 | 3 | ||
 Spain | Marta Marrero |  Italy | Antonella Serra Zanetti | 154 | 4 |
The following pairs received wildcards into the doubles main draw:
See main article: 2005 İstanbul Cup – Singles. Venus Williams defeated 
Nicole Vaidišová, 6–3, 6–2[1]
See main article: 2005 İstanbul Cup – Doubles. Marta Marrero / Antonella Serra Zanetti defeated 
Daniela Klemenschits / Sandra Klemenschits, 6–4, 6–0
Israel
Russian Federation
