Usain Bolt has announced he and girlfriend Kasi Bennett are expecting a child together.

The eight-time Olympic gold medallist, who retired from athletics after the 2017 World Championships, revealed the news on Thursday.

He wrote on his social media accounts: "I just want to say a KING or QUEEN is about to be HERE."

Bennett added on Instagram: "Our golden child. Coming soon..."

She called the news "our biggest blessing" and captioned an image of herself holding a bunch of balloons with the comment: "Our greatest celebration..."

She was portrayed in a billowing red dress by the sea in an unidentified location, cradling a baby bump.

Bennett wrote on Bolt's birthday last August that the 33-year-old was "the man who has taught me how to live life to the fullest, work for it don’t just wish for it and don’t stop until you exceeds limits and break records".

She described him as "pure gold" and added: "You are one the world needs, I need - so continue to inspire us and show us how to be humble, kind and successful."

Bolt is the world record holder for the 100 metres and 200m and regarded widely as the greatest sprinter in history.

After athletics, he attempted to forge a career in football but was released by Australian club Central Coast Mariners in November 2018 after a short trial with the team.

I just want to say a KING or QUEEN is about to be HERE. @kasi.b

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