During his stint as the finance minister in the early 1990s, the suave, soft-spoken Sikh guided India out of financial trouble and put the country on course to becoming an economic power.
After Sonia Gandhi – the triumphant leader of the Congress party - decided not to become India's prime minister, Singh emerged as the next best choice for the position.
In 1991, Singh became India's finance minister and made an immediate mark.
India's economy was then in shambles, suffering from an unsustainable fiscal deficit of 8.5% of the gross domestic product. The country also seemed to be sinking under a huge balance of payment deficit.
But Singh undertook the huge task of restructuring the economy.
Under his tutelage, the tax system was rationalised. Many controls and regulations that saddled Indian business were scrapped and entrepreneurs found themselves empowered with new business freedoms. Productivity jumped and the industry grew in unprecedented leaps.
Years later, India's industry captains still look to Singh with reverence and gratitude.
And there is a general expectation that with the ''reformist'' back at the helm, India's economy will be in safe hands.
Gandhi also has reasons to feel safe with her choice.
A politician with no mass base, Singh poses no political threat to her and the Congress president can hope to retain all her power and authority.
The low-profile Singh will now find himself as the prime minister of the world's most populous democracy.
Born in West Punjab in 1932, Singh holds a degree from Oxford University.
He made his mark as a bureaucrat and was the governor of the Reserve Bank of India before his induction into politics.