The idea of Amazon, a company founded 23 years ago on the premise of shopping from the comfort of a computer screen, moving forcefully into the crowded field of brick-and-mortar retail, with its limitations on selection and lack of customer reviews, once seemed ludicrous. But in the past several years, the company has dabbled with stores, opening or planning more than a dozen bookstores around the country.
In Seattle, it recently opened two grocery drive-through stores where customers can pick up online orders, along with a convenience store called Amazon Go that uses sensors and software to let shoppers sail through the exits without visiting a cashier.
The addition of Whole Foods takes Amazon’s physical presence to a new level. The grocery chain includes more than 460 stores in the United States, Canada and Britain with sales of $16 billion in the last fiscal year. Mikey Vu, a partner at the consultancy Bain & Company who is focused on retail, said, “They’re going to be within an hour or 30 minutes of as many people as possible.”
Founded in 1978 in Austin, Tex., Whole Foods is best known for its organic foods, building its brand on healthy eating and fresh, local produce and meats. It has also long been caricatured as “Whole Paycheck” for the high prices it charges for groceries. That conflicts with a core tenet of Amazon, which has made low prices part of its mission as a retailer.
Analysts speculated that Amazon could use its $99-a-year Prime membership service, which gives customers free, two-day shipping and other benefits, to offer Whole Foods customers a better price on groceries, as it does for books in its bookstores. The stores could also serve as an advertisement to get more customers to sign up for Prime; in September the financial firm Cowen & Company estimated that Prime had 49 million subscribers in the United States, representing about 44 percent of households.
Amazon has been on a multiyear offensive to open warehouses closer to customers so it can deliver orders in as little as two hours, and Whole Foods stores will further narrow Amazon’s physical proximity to its shoppers. The stores could become locations for returning online orders of all kinds. Amazon could also use them to cut delivery times for online orders.
The $13.4 billion deal, which does not include net debt, immediately raised questions about whether Amazon’s experiments with automation, like the cashier-less checkout technology it is testing in its Amazon Go store, could eventually lead to job losses at Whole Foods stores.
“Amazon’s brutal vision for retail is one where automation replaces good jobs,” Marc Perrone, president of the United Food and Commercial Workers International Union, said in a statement. “That is the reality today at Amazon, and it will no doubt become the reality at Whole Foods.”
Drew Herdener, a spokesman for Amazon, said it has no plans to use the Amazon Go technology to automate the jobs of cashiers at Whole Foods and no job reductions are planned as a result of the deal. Whole Foods workers are not unionized.
The move to buy Whole Foods is a further sign of the outsize ambitions of Jeff Bezos, Amazon’s chief executive and founder, who came under fire from Donald J. Trump during the presidential campaign last year, when Mr. Trump said Mr. Bezos had a “huge antitrust problem because he’s controlling so much.”
Nicole Navas Oxman, a spokeswoman for the Justice Department, declined to comment about whether its antitrust division saw any issues with the proposed acquisition. Law professors who specialize in antitrust said it was unlikely regulators would block the deal.
“One question would be, does an online seller of groceries compete with a brick-and-mortar grocery store, and I think the answer is ‘yes, at some level, but that overlap is probably not terribly great,’” said John E. Lopatka, a professor of antitrust law at Penn State University.
If the deal goes through, Amazon and Whole Foods will still only account for about 3.5 percent of grocery spending in the United States, making it the country’s fifth largest grocery retailer, according to estimates by John Blackledge, an analyst at Cowen & Company.
Groceries are purchased five times a month on average by shoppers, compared with the four times a month Amazon Prime customers typically shop on the site and two times for people who do not have Prime memberships, Cowen estimates.
“If you open up groceries, it could increase the frequency,” Mr. Blackledge said.
For Whole Foods, the deal represents a chance to fend off pressure from activist investors frustrated by a sluggish stock price as it has faced fierce competition from Costco, Safeway and Walmart, which have begun offering organic produce and kitchen staples, forcing Whole Foods to slash prices. Money managers, unhappy with the pace of the turnaround effort, have pushed for more, taking aim at the board, its grocery offerings and its pricey real estate holdings.
In response, Whole Foods has revamped its board and replaced its chief financial officer. Gabrielle Sulzberger, a private equity executive, was named the company’s chairwoman. Ms. Sulzberger is married to Arthur O. Sulzberger Jr., the chairman and publisher of The New York Times.
Investors are betting there may be other buyers interested in Whole Foods, and by late Friday the company’s shares rose above Amazon’s $42 a share offer.
Even with the bigger physical presence Amazon will gain through Whole Foods, it will have far less reach than Walmart and its Sam’s Club warehouse chain, which together account for about 18 percent of the grocery market. Walmart has almost 10 times the number of stores as Whole Foods does.
“We feel great about our position, with more than 4,500 stores around the country and fast growing e-commerce and online grocery businesses,” Greg Hitt, a spokesman for Walmart, said in a statement.
An earlier version of this article misstated the annual sales in the United States in the grocery industry. The sales are $700 billion to $800 billion, not $700 million to $800 million.