Athina Onassis de Miranda was born on the 29. January 1985 in Neuilly-sur-Seine, France, as is the only child of Christina Onassis (1950–1988) and her fourth husband, Thierry Roussel. Athina is the only grandchild of Aristoteles Onassis, the Greek shipping magnate. After her mother's death, she was raised by her father and his second wife. For her early education, she attended a school in Lussy-sur-Morges (Switzerland). Following a preparatory course in Brussels she passed her baccalauréat exam in the summer of 2003.
Athina began her equestrian career as a teenager, when she was still known as Athina Roussel. Her coach was the famous Nelson Pessoa, father of Rodrigo Pessoa, one of the world’s best riders. At Pessoa´s horse center in Brussels she met Doda. They married on December 3rd 2005 in Sao Paolo. Athina then switched her national affiliation from France to Greece, effective for all of her equestrian competitions. Athina is an international showjumping rider and also the patroness of the Athina Onassis International Horse Show, established in 2007. Athina and Doda are joint owners of AD Sport Horses.