Cristiano Ronaldo's underwear company in legal trouble!

Real Madrid and Portugal superstar Cristiano Ronaldo is also known to fans by the shorthand CR7, prompting the company behind his line of sleek underwear to target a Rhode Island man who has trademarked the letter-number combination, according to a new lawsuit.

In a complaint filed on Monday in Rhode Island federal court, 43-year-old fitness enthusiast Christopher Renzi said he had received letters from lawyers for the Danish company JBS Textile Group demanding he give up the trademark because it had “imminent plans” to enter the U.S. market with Ronaldo's CR7 underwear.

JBS has also asked the U.S. Patent and Trademark Office to cancel Renzi's trademark, according to court documents. Renzi is seeking the court's declaration that he owns the trademark.

“We just want them to leave us alone,” said Renzi’s attorney Michael Feldhuhn.

Attorneys for JBS could not be reached for comment.

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Renzi registered the moniker in 2009 and has put it on jeans and T-shirts, Feldhuhn said. He also has a website advertising a seven-minute fitness workout, also under the CR7 name.

According to the complaint, Renzi adopted the mark based on his initials and the day he was born, October 7.

Court materials showed that JBS, which said it holds the “exclusive, worldwide license” to market Ronaldo’s CR7 underwear, believed Renzi trademarked CR7 specifically to profit from Ronaldo’s soaring fame.

CR7 was “so closely tied to the fame and reputation of Cristiano Ronaldo, that a connection with the soccer player would immediately be presumed by the general public when encountering” Renzi’s branded clothes, said JBS’s filing with the Trademark Trial and Appeal Board.

The 29-year-old Ronaldo is one of the most highly paid and recognisable athletes in the world. He has marketing deals with numerous major companies. His Facebook page has more than 93 million "likes."

One of his latest postings shows a behind-the-scenes underwear photo shoot for a CR7 campaign launching “next week.”

Besides underwear, his brand is already expanding into shirts and shoes.

Ronaldo is a more famous user of CR7, Feldhuhn said, “but it’s really based on who’s using it first. We can show we were the first use of the CR7 name in commerce in America.”

Feldhuhn added, “They don’t really have the trademark rights because they haven’t used it.”

The case is Christopher Renzi v. JBS Textile Group A/S and Cristiano Ronaldo a.k.a. Cristiano Ronaldo Dos Santos Aveiro, U.S. District Court for Rhode Island. Case No. 14-cv-00341.