The couple welcomed Kaya Klitschko on Tuesday and the newborn weighed a healthy 7 lbs., 14 oz., and measured 20 inches.
Hayden Panettiere gave birth to her first child on Tuesday
"We are over the moon and madly in love!," the new parents revealed.
Coming up with a name for their little princess was difficult given that it had to work both in the States, Ukraine, where Wladimir is from and Germany where he lived for many years.
The couple were introduced by friends in 2008 and dated for three years before breaking up because of their conflicting schedules. Hayden, 25, is best known as the star of TV series Heroes and Nashville.
Hayden,25, is engaged to boxer Wladimir Klitschko
The 6ft 6in athlete has a demanding career of his own. Waldimir, 38, is the second longest reigning heavyweight champion of all time and earned $24 million in 2013, according to Forbes magazine.
That year the unlikely duo reconnected leading Hayden to tell one magazine: "It's like the 2.0 version."
Shortly afterwards, the boxing champion presented her with a large diamond. Hayden coyly refused to reveal the circumstances of their engagement beyond confirmed that her beau had indeed proposed.
Hayden and Wladimir have named their baby girl Kaya
Having reunited, starting a family seemed like a natural step for Hayden.
She said: "Motherhood is the most beautiful, exciting thing, and there's nothing that I feel like I can't accomplish while having children in my life.
"I would sacrifice having more years of being wherever I want whenever I want for years with my kids."