He will help drive greater environmental action and awareness, and advocate for the goals of UN Environment's global BreatheLife campaign, Paytm said in a statement.
The campaign will work on promoting policy and citizen action for better air quality for people.
"I am honoured to be appointed UN Environment Patron of Clean Air. We can't achieve economic well-being without ensuring the well-being of the environment," Sharma said.
The private sector is key to ensuring cleaner air and a more sustainable future for all, he added.
With his appointment, Sharma joins Patron of the Oceans Lewis Pugh (British swimmer) and Wilderness Patron Ben Fogle (Broadcaster) in the prestigious list.
"Tackling pollution requires all of us, citizens, governance and business to come together. We need more champions in the private sector like Mr Sharma to drive innovation that will get us to a cleaner future," said Erik Solheim, head of UN Environment.