Rivian, a maker of electric trucks and vans, is going public at a stock price that values the company at nearly $70 billion, a remarkable number that highlights the belief on Wall Street that the fast-growing electric vehicle market is still a wide-open field.

In a securities filing on Tuesday, Rivian said it was selling its shares in the offering at $78. At that sum, it will raise nearly $12 billion. That fund-raising figure would surpass Uber, which raised $8 billion from its I.P.O. in 2019.

Rivian stock will start trading Wednesday on the Nasdaq exchange under the ticker RIVN. At close to $70 billion, Rivian’s market capitalization would approach that of Ford Motor, which is valued at $80 billion and sold more than four million vehicles worldwide last year.

The market environment for the offering has been shaken this week as shares in Tesla, the leading electric-car maker, plunged after its chief executive, Elon Musk, said he might sell some of his stock.

Rivian has a huge appetite for cash. Before this I.P.O., it raised over $10 billion from investors including Amazon and Ford, and it expects to consume billions of dollars as it tries to ramp up production of its three vehicles: an upscale pickup truck aimed at drivers who like off-roading; a sport utility vehicle; and a delivery van that was developed with Amazon, which has a significant stake in Rivian and has ordered 100,000 of the vans.

Rivian and many other automakers are betting that consumers are prepared to shift rapidly to electric vehicles over the next decade. General Motors has said it aims to phase out production of gasoline-powered vehicles by 2035. Tesla, which is on track to sell nearly one million electric vehicles worldwide this year, has a $1 trillion market capitalization, exceeding the combined value of G.M., Ford, Toyota Motor, Volkswagen, BMW and several other automakers.

Much now depends on whether Rivian can scale up its production to meet customers’ orders. Tesla went through many rocky months when it struggled to produce its sedan in large numbers.

By the end of last month, Rivian had delivered only 156 of its pickups, known as the R1T; it plans to start deliveries of the S.U.V., the R1S, next month. It said in a financial filing that it did not expect to fulfill the 55,400 orders for the truck and S.U.V. until the end of 2023, underscoring that it would take time to get production lines churning out significant numbers of vehicles.

Like other electric vehicle makers that have gone public this year, Rivian is reporting large losses. In the first six months of this year, it had a net loss of $994 million, almost as much as in all of 2020, when it lost $1.02 billion. Investors may be willing to tolerate the losses for some time. The van contract with Amazon should in theory secure a steady revenue stream.

And Rivian may also benefit from the view in the auto sector that it is well run. Its chief executive, R.J. Scaringe, has a doctorate in mechanical engineering from the Massachusetts Institute of Technology and, so far, has not shown himself to be easily distracted or the source of unnecessary controversies, criticisms made of Mr. Musk of Tesla.

Rivian’s pickup and S.U.V. are focused on well-to-do buyers who like the outdoors. “Keep the world adventurous forever,” Rivian’s I.P.O. prospectus proclaims.

Still, Rivian will face daunting competition, including established automakers that have much experience with mass production. Next year, Ford is supposed to start producing an electric version of its F-150 pickup truck, the top-selling vehicle in the United States. G.M. is expected to soon begin selling an electric GMC Hummer — in both truck and S.U.V. versions — and is working on a Chevrolet Silverado electric pickup.

At the I.P.O. price, Rivian will be valued even higher, at around $75 billion, if its bankers sell extra shares they have on hand to meet strong demand and some stock issued as compensation to employees is included in the calculation.