Microsoft struck a 10-year deal with Reliance in 2019, committing to power the oil-to-telecoms conglomerate's data centres with its Azure cloud.
"We've been working with Reliance across the entire stack - everything from what they are going to be doing with Azure in their own data centres and how they will extend it," said India-born Nadella at the event in Mumbai, where he began the first leg of his India tour.
"It's sort of a great example of a business leader and a company which is in very diverse sectors to take a platform approach, to use technology to create more technology."
The executives did not provide specific details about their growth plans.
"We're very excited about the partnership that Jio (Reliance's telecoms unit) and Microsoft will have and I think that will be, as we look at this decade, a defining partnership," Ambani said.
During a keynote speech earlier, Nadella emphasised the need for businesses to build their own technology at a time digital services are transforming all industries, and even homes.
Nadella visits his home country just weeks after telling Buzzfeed News that India's new citizenship law saddened him and was "just bad".
India's Citizenship Amendment Act, which paves a way for minorities from neighbouring Muslim-majority nations of Pakistan, Afghanistan and Bangladesh to gain citizenship, has sparked weeks of protests.
Critics say that the law, combined with a proposed national register of citizens, will discriminate against India's Muslims minority.
Nadella, who did not broach political issues at Monday's event, will also travel to the southern tech hub of Bengaluru and the Indian capital New Delhi.
(Reporting by Nupur Anand; Writing by Sankalp Phartiyal; Editing by Alexandra Ulmer and Raju Gopalakrishnan)
By Nupur Anand
