India's first woman president since the country gained independence from British rule 60 years ago has taken office in Delhi.
Mrs Patil's backers say her election will be a boost to women
Pratibha Patil, 72, was sworn in as head of state in a ceremony at the Indian parliament.
Mrs Patil's supporters say her election to the largely ceremonial role will be a boost to millions of Indian women.
She succeeds APJ Kalam who urged Indians to transform their country into a fully developed nation by 2020.
Mrs Patil won a comprehensive presidential election victory, mopping up nearly two-thirds of votes cast in state assemblies and in India's parliament.
Dressed in a white and green sari draped over her head, Mrs Patil took the oath of office.
In her inaugural speech in parliament, she promised to uphold the constitution and devote herself to the people of India.
A 21-gun salute greeted the new president.
Her cavalcade arrived at the parliament escorted by soldiers on horse back, dressed in white.
Mrs Patil, the former governor of the northern Indian state of Rajasthan, earlier described her election as "a victory for the principles which our Indian people uphold".
Members of India's governing Congress Party say her victory is an important step towards gender equality in India.
But many say it is only a symbolic gesture in a country where millions of women face discrimination often linked to traditions.
Mrs Patil emerged as a surprise, last-minute candidate after left-wing parties in the Congress-led coalition opposed the Congress Party's first choice.
She was backed by Congress leader Sonia Gandhi, but was mocked by opponents and by some sections of India's media.
Mrs Patil has courted controversy, recently telling a Muslim congregation that the veil was introduced to protect their women from Mughal invaders, a comment she later retracted.
She also faced allegations that a bank she helped set up gave out cheap loans to her relatives before it folded.
The Congress Party has rejected those allegations.
The presidency is largely a ceremonial post, but plays a key role with a fragmented electorate often throwing up precariously placed coalition governments.