The list of 72 most powerful people in the world also included the names of Reliance Industries Chairman Mukesh Ambani at 36th, ArcelorMittal Chairman and CEO Lakshmi Mittal at 57th and Microsoft's Indian-born CEO Satya Nadella at 64th.
On Modi, Forbes said "India's newest rock star doesn't hail from Bollywood. He is the newly elected Prime Minister who sailed into office in May with a landslide victory, ushering the Bharatiya Janata Party (BJP) into power after decades of control by the Gandhi dynasty."
"Modi is credited with massive reconstruction projects in his home state of Gujarat. His administration promises to bring economic rejuvenation to other beleaguered parts of India. The world is as impressed as the citizens of India: So far he's toured the US and China and met with his Southeast Asian neighbours," the magazine said.
This year there are 12 newcomers on the list, including Modi and Egypt President Abdel el-Sisi.
Alibiba founder and China's richest man -- Jack Ma also makes a first appearance on the list after his record-breaking USD 25 billion initial public offering in September, as does terror group Islamic State's chief Abu Bakr al-Baghdadi.
The next Indian after Modi on the list is Ambani at 36th.
Forbes said Ambani has business ventures in petrochemicals, manufacturing, oil and gas production, and now wireless sectors, "the sum of which have landed him as the richest person in India for eight years running."
It noted Reliance's USD 655 million acquisition of media outfit Network18.
In October, Modi inaugurated Ambani's Reliance Foundation's new hospital in Mumbai, "ending rumours about Ambani's waning clout in New Delhi," it said.
The top five remain the same as 2013 -- Chinese President Xi Jinping ranked third, Pope Francis at No. 4 and the world's most powerful woman German Chancellor Angela Merkel ranked fifth.
