By Promit Mukherjee and Alexandra Ulmer
MUMBAI, Aug 12 (Reuters) - India's Reliance Industries Ltd RELI.NS is set to sell a 20% stake in its oil to chemicals business to Saudi Aramco in one of the largest foreign investments in the country, Reliance Chairman Mukesh Ambani said on Monday.
"(This is) the biggest foreign investment in the history of Reliance," Ambani said at the company's annual general meeting in India's financial capital Mumbai.
"It is also amongst the largest foreign investments ever in India."
The deal valued the business at $75 billion including debt, he said.
Saudi Aramco, the world's biggest oil producer, has been in talks with Reliance on the stake sale as it plans to secure new markets for its crude.
Saudi Aramco will also supply 500,000 barrels a day of crude oil on a long-term basis to RIL's Jamnagar refinery, Ambani said.
"This signifies perfect synergy between the world's largest oil producer and the world's largest integrated refinery and petrochemicals complex," he added.
The partnership will cover all of Reliance's refining and petrochemical assets, including its 51% stake in the petroleum retail joint venture, he said.
Last week, Reliance announced that it was forming a fuel retailing joint venture with global oil major BP BP.L in which Reliance would own a 51% stake.
(Reporting by Promit Mukherjee and Alexandra Ulmer; Writing by Abhirup Roy; Editing by Sonali Paul and Stephen Coates)