Pénélope Julie "Diddie" Vlasto Serpieri (French pronunciation: [ʒyli vlastɔ]; 8 August 1903 – 2 March 1985) was a female tennis player from France.

She won the silver medal at the Paris Olympics in 1924 in women's singles,[1] losing the final to the American Helen Wills Moody.

She was born as Pénélope Julie Vlasto on 8 August 1903, in Marseille, France.

According to Wallis Myers of the Daily Telegraph and Daily Mail, Vlasto was ranked in the world top ten in 1923 and 1926, reaching a career high of world No.

The World Hard Court Championships (WHCC), actually played on clay in Paris or Brussels, began in 1912 and were open to all nationalities.