India's Tata Motors market cap crossed the 1 trillion rupees ($18.23 billion) mark, joining what is now a 14-member club that also includes Reliance Industries Ltd, Oil and Natural Gas Corporation Ltd and Tata Consultancy Services Ltd.
Tata Motors shares have hit a record high this year after surging 4.7 percent as of Wednesday's close, adding to its 75 percent gain in 2012.
Signs of improving sales at its unlisted unit Jaguar Land Rover and the improving economic outlook in its key China market have bolstered the auto maker's shares, analysts said.
The 1 trillion rupees market cap includes differential voting rights and common shares.
Tata Motors shares are up 1.83 percent as of 0858 GMT. ($1 = 54.8550 Indian rupees)
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