Polona Hercog (Slovene pronunciation: [pɔˈlóːna ˈxèːɾtsɔk], born 20 January 1991) is a Slovenian professional tennis player.

Partnering with Jessica Moore, she won the French Open and Wimbledon Championships junior titles in the doubles competition in 2008.

[1] As a four-year-old she began playing in the local tennis clinic opened by Mima Jaušovec, and at age 14 moved to Italy to train professionally.

In doubles, she and Australian Jessica Moore won two Grand Slam titles together, the French Open and Wimbledon; the latter was the final tournament of her junior career.

In September 2007, Hercog received a wildcard and made her WTA Tour debut at the Slovenia Open, losing to Elena Vesnina in three sets.

Hercog then participated in the İstanbul Cup, coming through qualifying to reach the main draw, where she lost in the first round to eighth seed Tsvetana Pironkova.

215, she made her Grand Slam debut in the qualifying competition of the US Open, losing to Sandra Záhlavová in the first round.

At that year's French Open, she qualified for the main draw and upset 23rd seed Kleybanova before losing to Aravane Rezaï in the second round.

[7] Partnering with Barbora Záhlavová-Strýcová, she won her first tour doubles title, beating the Italian duo Sara Errani and Roberta Vinci.

Seeded sixth at the Danish Open in Copenhagen, she had a chance to take revenge on Anna Chakvetadze as they met in the quarterfinals.

She retired trailing 6–1, 4–1 in her first-round match against seventh seed Anastasia Pavlyuchenkova due to a low back injury.

[35] Seeded eighth at the Barcelona Ladies Open, Hercog retired in her first round match against Sorana Cîrstea after losing the first set 4–6 due to dizziness.

[42] Hercog then played at the Swedish Open as the defending champion and prevailed again, defeating Mathilde Johansson in the final.

[43] Representing Slovenia at the London Olympics, Hercog was defeated in the first round by María José Martínez Sánchez.

[86] Seeded 20th for qualifying at the Cincinnati Open, Hercog reached the main draw beating Paula Ormaechea and Julia Glushko.

[96] Seeded seventh at the Rio Open, Hercog was defeated in the second round by Brazilian wildcard Beatriz Haddad Maia.

[99] Getting past qualifying at the Indian Wells Open, Hercog beat 2009 champion Vera Zvonareva in the first round.

[citation needed] Seeded seventh at the Bol Ladies Open, Hercog reached the final which she lost to Mandy Minella.

[116] Beginning her grass-court season at the Rosmalen Open, Hercog retired during her first-round match against Varvara Lepchenko.

[119] Competing at the Bucharest Open, Hercog made it to the quarterfinals where she was defeated by fourth seed Laura Siegemund.

[121] Representing Slovenia at the Rio Olympics, she lost in the first round to eventual gold medalist Monica Puig.

Seeded seventh at the Internazionali di Brescia, she won the title, defeating Ganna Poznikhirenko in the final in two sets.

[130] As the top seed at the Andrézieux-Bouthéon Open, Hercog reached the semifinals where she retired after losing the first set against Rebecca Šramková.

[134] Since Caroline Wozniacki withdrew from the tournament due to a viral illness, she got a lucky loser spot in the main draw.

Even though she lost in the final round of qualifying to Laura Siegemund, she still entered the main draw as a lucky loser.

[137] Hercog won her third WTA singles title at the Ladies Open Lugano, defeating Iga Świątek in the final.

[144] At the Prague Open, she lost in a tight three-set first-round match to top seed and eventual champion, Simona Halep.

Hercog started her season at the first edition of the Abu Dhabi Open where she lost in the first round to fourth seed and eventual champion, Aryna Sabalenka.

[157] Despite losing in the final round of qualifying at the Madrid Open to Bernarda Pera, she still received a lucky loser spot into the main draw due to the withdrawal of Svetlana Kuznetsova.

Finally, she lost in the first round of the Indian Wells Open to Anastasija Sevastova, making her win–loss record 4–14 for the season, the worst in her 15-year professional career.