Rivian, which counts Ford Motor Co and T. Rowe Price among its investors, registered the IPO confidentially with U.S. regulators last month. It is seeking a valuation of about $80 billion in the listing, which is expected to land in late October or November, the sources said.

Rivian declined to comment.

If Rivian raises $8 billion in the IPO, that would rank as the fourth biggest of the past decade in the United States. Only three other companies have raised more than $8 billion in IPOs since 2011, according to Dealogic: Alibaba, which raised a world-record $25 billion in 2014; Facebook, which raised $16 billion in 2012; and Uber, which raised $8.1 billion in 2019.

Proceeds from the IPO will allow Rivian to expand production beyond its assembly plant in Normal, Illinois. The startup has said it is in talks with multiple locations to build a second U.S. factory, which documents viewed by Reuters show would include an investment of at least $5 billion.

Rivian has not provided details on its IPO plans, but it is expected to reveal its finances for the first time in a public filing in the coming weeks.

California-based Rivian is among the most well-funded U.S. startups, having raised $10.5 billion since the start of 2019. Other investors include BlackRock Inc, Soros Fund Management, Fidelity and Saudi auto distributor Abdul Latif Jameel Co (ALJ).

While Rivian has been dubbed as the "Tesla killer" in some quarters, it is still tiny compared with Tesla Inc, which boasts of a market cap of nearly $740 billion and plans to build a pickup truck that would compete with Rivian's own version, the R1T.

Rivian's flotation is expected to round out another record year for U.S. IPOs. Companies have raised more than $230 billion so far this year through share sales, according to data from Dealogic, and are on track to raise tens of billions more before the year ends.

Founded as Mainstream Motors in 2009 by Chief Executive R.J. Scaringe, the company changed its name to Rivian in 2011. "Rivian" is derived from "Indian River" in Florida, a place Scaringe frequented in a rowboat as a youth.

(Reporting by Ben Klayman in Detroit and Anirban Sen in Bengaluru; Editing by Steve Orlofsky)

By Ben Klayman and Anirban Sen