When you know, you know.

Nick Kyrgios proudly declared in a new interview with The Daily Telegraph that girlfriend Costeen Hatzi is “definitely the one,” as he opened up about the couple’s burgeoning romance.

“She is definitely the one, I am in love with her and she is an amazing person,” Kyrgios said, according to the Daily Mail, with the Australian tennis star later adding, “We go through ups and downs together but I love her to bits.”

Kyrgios and Hatzi, a fashion blogger, made their relationship public late last year. In recent months, the 27-year-old athlete — who had a messy split from ex-girlfriend Chiara Passari in October 2021 — has continuously expressed his love for Hatzi in interviews, telling The Daily Telegraph how much her support has meant to him.

“I guess for me as an athlete, just to know that I have got that person there that can overcome and have that shoulder to lean on whenever I need, that is what I love about her,” he said.

Hatzi has traveled the globe with Kyrgios as he competes in various tournaments, including the Miami Open in March. The couple even sparked engagement rumors last month after posting ring emojis on social media.

With Wimbledon just around the corner, it’s likely Hatzi will be jetting to London with Kyrgios, who recently told The Sydney Morning Herald that he’s the best grass-court player in the world.

Much like Kyrgios, Hatzi has also given candid takes on her personal life, noting in March that she’s still adjusting to life in the spotlight.

When asked about the travel with Kyrgios and the change of lifestyle, Hatzi said during an Instagram Q&A that “it was a little overwhelming at first but I’m definitely getting use [sic] to it.”

“Nicks team is so friendly and we’re all supportive so it works well when we travel,” she continued.