Serena Williams and Alexis Ohanian have named their baby girl after her father.

Serena Williams and her baby (c) Instagram

Serena Williams and her baby (c) Instagram

The 35-year-old tennis ace and her fiance welcomed a little girl into the world on 1 September, and the sportstar has now revealed her daughter is called Alexis Olympian Ohanian Jr..

However, it seems the baby may go by her middle name as the Reddit co-founder referred to her that way on his Instagram account.

He posted: "Welcome, Olympia, we're so happy to meet you. We made you a video of our adventure together so far (sic)".

Serena has shared the first picture of the tot on her Instagram page, and also revealed she had experienced "complications" that led to them staying in hospital for around a week.

She said in a clip on her Instagram Stories: "So we're leaving the hospital after six, seven days.

"It's been a long time, but we had a lot of complications, but look who we got -- we got a baby girl!"

The couple also shared a montage of special moments from Serena's pregnancy, including her first ultrasound scan, bump selfies and her and Alexis assembling the nursery.

The sportswoman also quipped about her baby having already got a Grand Slam title to her name, as Serena won the Australian Open during the early stages of her pregnancy.

Meanwhile, Serena's older sister, Venus Williams, recently admitted she is "super excited" about the new addition to their family.

Speaking at the US Open, Venus said: "I'm super excited. Words can't describe."

Speaking after her third-round match win against Greece's Maria Sakkari, Venus claimed she wouldn't be answering questions about her sister's start to parenthood, but did admit the pair "always talk".

She said: "We always talk. We always talk, so she's always encouraging me. Yeah, from every step of the way, every match, always."