Sears is filing for bankruptcy after years of crushing debt. (SHANNON STAPLETON/Reuters)

Sears, the one-time titan of American retail, filed for bankruptcy ahead of a $134 million debt payment due Monday.

For years, Sears has contended with the threat that it would become the latest big-name retailer to fall to online competition and crushing debt. The icon once known for its pristine catalogs, and more recently known for decrepit showrooms and a controversial chief executive, saw its stock price plunge last week after reports that it had hired an advisory firm to prepare a bankruptcy filing ahead of the Oct. 15 payment.

A personal familiar with the negotiations told The Post late last week that Sears planned to file a Chapter 11 bankruptcy filing, which would allow it to reorganize and possibly reemerge from bankruptcy with some part of the business intact.

The company had been in talks about securing special financing known as a debtor-in-possession loan of several hundreds of million dollars to carry it through the bankruptcy period while it restructures its debt and reorganizes its business. That loan would come from creditors, including banks such as Bank of America, Wells Fargo and Citi Group. The person estimated that roughly 150 stores would close immediately.

“And the intention is to bring the company out on the other side,” the person said.

The stock price was 41 cents a share when trading ended Friday.

The 125-year-old retailer was hardly the first to crumble while saddled with cavernous showrooms as e-commerce competitors soared. The company has roughly $5.6 billion in outstanding debt and has dwindled down to about 820 Sears and Kmart stores, down from 2,000 five years ago. It has also already sold off many of its brands, including Craftsman tools, and hasn’t turned a profit since 2010. Many of its most valuable properties have been sold off, with the other half leased and offering little cost savings from rent restructurings since Sears already pays below market rents.

One bankruptcy expert described Sears’ downfall as “the slowest-moving train wreck." But any movement toward bankruptcy seemed to gain momentum last week with reports that Sears had hired New-York based M-III Partners to prepare the filing. Sears recently added a restructuring expert as a company director for an additional layer of guidance on how to navigate a bankruptcy filing.

Still, it was unclear whether the company would attempt some other restructuring plan and whether chief executive Eddie Lampert would devise another plan to save the company he took over in 2013.

In September, Lampert — Sears’ largest shareholder and creditor and the owner of the hedge-fund ESL Investments — asked creditors to refinance $1.1 billion in debt before the Oct. 15 payment, according to a filing with the Securities and Exchange Commission. He also called on the company to sell off $3.25 billion in real estate and assets. Those include Sears Home Services and the company’s flagship Kenmore brand, which Lampert offered to buy in August for $400 million.

Lampert has often attempted to keep Sears viable with loans. Much of his focus has turned to Sears’ online presence over upkeep on physical storefronts, many of which total thousands of square feet. Lampert bought Sears in 2004 and merged it with Kmart, in which he had a controlling stake, the next year.

Lampert himself has had a controversial tenure at Sears. Paula Rosenblum, co-founder of Retail Systems Research, wrote in Forbes that Lampert would emerge from a Sears bankruptcy as the least-sympathetic victim and perhaps the largest beneficiary. Lampert learned long ago that he could make money from from selling off some of the company’s signature brands, like Craftsman tools and Lands End. Plus, in bankruptcy proceedings, the largest creditors become the owners of the new entity.

Rosenblum told The Post that those with the most to lose from Sears’ end will be the workers who stand to lose their pensions and jobs. And malls and shopping centers — ultimately left with huge empty warehouses — will have to get creative about new ways to clinch foot traffic. Options could range from food halls to pop-up stores to Tonya-Harding-esq skating rinks, Rosenblum said — so long as the concept was about more than just shopping.

Still, even given Lampert’s mismanagement and Sears’ drawn-on decline, Rosenblum distilled the company’s downfall to one word: tragedy.

“Here you have what was the original Amazon on steroids,” Rosenblum said. “This is a proud American institution, and what he’s done to it is embarrassing. It just is.”