Portuguese President Anibal Cavaco Silva's office announced Gaspar's resignation on its website and said he will be replaced by Secretary of State for the Treasury Maria Luis Albuquerque. Prime Minister Pedro Passos Coelho's office confirmed Gaspar's departure in an email.
Neither statement gave specific reasons for Gaspar's resignation.
Gaspar was a key member of the government as it struggles to repair its finances after needing a 78 billion euro (USD 102 billion) rescue two years ago. He was an economist who previously worked at the European Central Bank and had no political career before joining the government following its election in June 2011.
But Gaspar's exit is unlikely to herald big policy changes.
The austerity program is a requirement of the bailout creditors -- the International Monetary Fund and other EU countries. If Portugal doesn't stick with the planned cuts and tax hikes the creditors can stop disbursements of the bailout funds, likely making it hard for the country to pay wages and pensions.