Yair Ramati, the head of Israel's missile defence programmes, has been sacked for a "grave breach of information security", according to the country's defence ministry.
He had committed “severe information security violations,” and "relevant authorities" were investigating, the ministry said.
No further details have been issued but reports in Israeli media said Mr Ramati had kept classified information on his personal computer.
A highly respected missile expert who had been working in the field since 1981, Mr Ramati oversaw projects such as the Iron Dome and Arrow anti-missile interceptor systems.