Skechers’ patented shoe design, left, compared to the L.L.Bean slip-on sneaker the Freeport company is being sued over. Screenshot from court filings

The third-largest footwear company in the world has filed a patent infringement lawsuit against L.L.Bean, claiming the Freeport retailer copied the “graceful, sweeping” design of the back of its shoes.

In the federal lawsuit filed in New York on Monday, Skechers USA said the Freeport-based retailer intentionally and willfully plagiarized the patented “Heel Cup” design featured on millions of Skechers sneakers.

“These designs are unique and eye-catching because they use graceful, sweeping, gently rolling lines and slopes to create the ornamental appearance of the heel of the shoe and make it visually appealing,” Skechers said in its complaint. “Rather than innovate and develop its own designs and a unique style for its footwear products, L.L.Bean chose to copy Skechers’ innovative design elements.”

Skechers patented its heel cup – which it said has broad appeal and was “instantly successful” –  in 2022. Its patents and trademarks are the California company’s “legal lifeblood,” it said.

The alleged offending shoe is L.L.Bean’s Freeport Slip-On, which retails online for $99. Screenshot from court filings

L.L.Bean only began making and selling a shoe with the same heel design after Skechers proved the popularity of the “novel and unique designs,” Skechers alleged.

The shoemaker said it is “continuously developing new shoe designs and advancing the state of the art.”

Its shoes have been “promoted by celebrities including Martha Stewart, Snoop Dogg, Doja Cat, Willie Nelson, Sugar Ray Leonard, Ringo Starr, Britney Spears, Carrie Underwood, Meghan Trainor, Tony Romo, Brooke Burke, Kim Kardashian, Howie Long and Robert Downey Jr.,” the company said in court documents.

Skechers declined to say whether it has sued other footwear retailers over heel cup patent infringement and said the company does not comment on pending litigation.

The offending shoes are not L.L.Bean’s famous Duck Boots, but rather the Freeport Slip-On shoes, which retail online for $99.

Skechers’ “slip in” shoes that appear to include the heel cup design range from about $70 to $105.

L.L.Bean did not respond to questions about the lawsuit.

Skechers is asking the court to bar L.L.Bean from selling shoes with the heel cup design and is seeking unspecified damages. The company has three weeks to respond and there is a pretrial conference Sept. 4.