Modi began the day with a visit to the Statue of Unity and the Sardar Sarovar Dam in Gujarat. The Statue of Unity was inaugurated by him on Sardar Vallabhbhai Patel's birth anniversary on October 31 last year.
"Alibaba founder Jack Ma says he was inspired by Modi. Leaving a mark on entrepreneurs, PM Modi indeed scripted a story that motivates most of us," tweeted one user.
"Happy bday Thalaiva.. @narendramodi," tweeted another.
His supporters and fans flooded the social media with their best wishes as several hashtags circulated on the micro-blogging platform.
"Prayers for ur good health and long life in service of the nation".
"We are safe in India because of you," said a Twitter user.
"Your vision for a healthier and cleaner India is an inspiration for all. May you always be blessed with good health in life,a said another.
"A Man with clear aVision', a man with specific amission', is here for a "reason," said another.
Another posted: "A man with white hair and white beard having more fans than superstars with 8 pack abs. A man who made politics more interesting than cricket and Bollywood in the country. A 69-year-old "youth icon".
Last year, PM Modi celebrated his birthday by spending time with schoolchildren in Varanasi.
"He won't celebrate his Bday in private jets & Indian Navy ships like other politic. Spiritual Mahan's always think about others and love to giving away. PM releases butterflies at the Butterfly park in Gujarat," posted another user.
Another said: "Wishing our rockstar a very happy birthday!
"From weakness to strength, you have been an inspiration to us. The knowledge you have imparted upon India has been a great asset. You are a true example of a living legend," said another Twitter user.
( With inputs from IANS )