No. 1 tennis player Novak Djokovic is engaged to Jelena Ristic, his girlfriend of eight years; "so happy!" Djokovic gushes on WhoSay. Credit: Andrew H. Walker/Getty

It must be love! Novak Djokovic is engaged to longtime girlfriend Jelena Ristic. The No. 1 tennis player announced that he's officially off the market on WhoSay and Facebook Wednesday, Sept. 25.

Djokovic, 26, posted a sweet photo of himself with his love of eight years giving him a kiss on the cheek. "Meet my fiancee and future wife. So happy!" he captioned the shot. "Thank you for wonderful wishes #NoleFam and friends!"

Posting the same photo on Facebook, he wrote, "Getting used to introducing Jelena as my fiancee and future wife. So happy!" His bride-to-be, the CEO of Novak Djokovic Foundation -- which serves to help children in need in Serbia -- also tweeted Wednesday, "Thank you all for wonderful wishes! #lucky #blessed #happy."

According to The Daily Mail, the Serbian couple, who live in Monte Carlo, plan to wed in 2014.

Djokovic has ranked World No. 1 by the Association of Tennis for 100 weeks, despite losing to Rafael Nadal at the US Open earlier this month. The two will compete in the China Open in Beijing next week. "I'm still No. 1 of the world in the rankings, but he has more chances to end up [at year's end] as No. 1," Djokovic told the ATP earlier this month. "Look, there are still tournaments to go. We'll see. I will just try to prepare myself for China."