The head of the fashion company - whose brands include Zara and Bershka - is the third most successful CEO in the world according to a global ranking by the Harvard Business Review (HBR).
The 2015 edition of the global CEO list saw Isla jump eleven places from last year, when he was named 14th best CEO in the global ranking.
Inditex, the world's largest fashion group, was founded by Spanish businessman Amancio Ortega in 1963 and opened its most famous store, Zara, in 1975.
Isla took over as CEO in 2005 and became Chairman of the group in 2011.
He studied law at Madrid's Complutense University and before joining Inditex was Chairman of the Altadis tobacco company.
Inditex reported a surge in profits in 2013-2014 as its key European markets began to recover from the financial crisis.
The rise brought its net profit to €2.5 billion ($2.65 billion), the group said in an earnings statement on its 2013-2014 financial year ending in January.
It said net sales rose eight percent to €18.12 billion, making it the biggest clothing company in the world by sales.
The company is currently expanding worldwide, opening 343 new stores in 2014, including in Shanghai and Miami, bringing its total to 6,683 stores worldwide.
During a press conference in March 2015, Isla told journalists that Inditex was keen to expand further.
"We continue to see huge growth opportunities in both western and eastern Europe," he said, adding that, "we believe that Inditex is in an excellent position to take advantage of global growth opportunities."
Isla, 51, who was born in Madrid, is joined on the top 100 list by two other Spanish CEOs.
Florentino Pérez Rodríguez, head of Spanish civil engineering company ACS (as well as Real Madrid football club president), comes in at number 13 and Iñigo Meirás, head of construction company Ferrovial, is at number 51.
But it was Danish CEO Lars Rebien Sørensen, the boss of insulin product company Novo Nordisk who was crowned the world's top performing CEO on the list.