Pénélope Julie "Diddie" Vlasto Serpieri (; 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, losing the final to Helen Wills Moody. Vlasto also won the version of the French national championships in 1924 that was open only to French nationals. She was a doubles partner of Suzanne Lenglen in many doubles tournaments during the early 1920s.
