Udaan, the fastest Indian startup to achieve the coveted unicorn status, has raised $373.5 million from new and existing investors in an ongoing Series D round. The business-to-business (B2B) online marketplace has raised the funds from Altimeter Capital, GGV Capital and Hillhouse Capital, besides existing investors DST Global and Lightspeed Venture Partners. Udaan is an online marketplace that facilitates buying and selling of fashion products, groceries and electronics among manufacturers, brands and retailers.