"I extend my full support to our hon Prime Minister @narendramodi ji's #SwachhataHiSeva mission. Cleanliness is godliness," Mr Rajinikanth tweeted.
The Kabali actor has been hinting for some time that he might join politics. His tweet comes a day after actor Kamal Haasan met with Delhi Chief Minister Arvind Kejriwal in New Delhi, amid speculation that he, too, might join politics.
Mr Haasan has said he would be willing to work with Mr Rajinikanth if the superstar decided to enter politics. The Swachhta Hi Seva campaign is being run during the fortnight from September 15 till Gandhi Jayanti on October 2.
Actors Akshay Kumar and Anushka Sharma and former cricketer Sachin Tendulkar have pledged support to the campaign.