Mera started fashion consortium Inditex in 1963 with Amancio Ortega, whom she married three years later.
The couple started off making women’s bathrobes but by 1975 had opened their first Zara store in La Coruña, northern Spain.
The company eventually expanded to sell eight different brands, including Massimo Dutti, Pull & Bear and Bershka.
With more than 6,000 stores in 86 countries, Inditex sales reached €15.9 billion ($21 billion) in 2012.
According to Bloomberg’s Billionaires Index, Mera’s estimated net worth was €4,1 billion ($5,5 billion), making her Spain’s wealthiest woman.
Although Mera and Ortega divorced in 1997, she held almost 7 percent of Inditex together with her daughter Sandra until her death on Thursday.
Mera, who dropped out of school at the age 11 to work as a sales assistant in a clothing shop, spent her last years running a foundation which helps disabled and disadvantaged people to find jobs.
Mera had two children, Sandra and Marcos, from her marriage to Ortega.