She submitted her resignation to President A P J Abdul Kalam in New Delhi.
"I have tendered my resignation as I am contesting for the Presidential poll," she added.
Later, talking to reporters, she expressed her gratitude to the President for his 'cooperation and guidance'. Patil said she wished him good health.
Image: Pratibha Patil speaks to the press at Rashtrapati Bhavan. To her right is Congress leader Jayanti Natarajan.
Photo credit : Raveendran/AFP/Getty Images