Rosalia Mera, who co-founded the Zara clothing shops, has died aged 69, the Spanish company that owns the fashion chain said.
Inditex SA did not give details about how Ms Mera, who was Spain's richest woman, died.
But Spanish media widely reported that she suffered a stroke while on holiday on the Mediterranean island of Menorca and died last night in a hospital she was taken to in north-western Spain.
Mr Mera was a seamstress who helped build Inditex from the clothing store she started with her then-husband, Armancio Ortega.
He is listed by Forbes as the planet’s third richest person. Ms Mera held 5.1 per cent of Inditex, and her fortune was estimated by Forbes at $6.1 billion.
The magazine said she was the world’s 195th richest person.