Katy Perry loses a trademark battle with a fashion designer called Katie Perry

• Pop singer Katy Perry lost a 15-year trademark battle with a clothing designer named Katie Perry.
• The "Teenage Dream" singer partially infringed the trademark of the designer's business.

Katy Perry lost a "David versus Goliath" trademark dispute brought by an Australian designer called Katie Perry, according to multiple reports.

Federal court judge Brigitte Markovic ruled that the "Teenage Dream" singer partially infringed the trademark of the designer's clothing business, according to documents released Thursday, Sky News reported.

"This is a tale of two women, two teenage dreams and one name," Markovic said in the judgment.

Sydney-based Katie Perry filed the lawsuit in 2019 and claimed the pop singer disregarded her trademark by selling clothing merchandise on her Australian tours between 2014 and 2018, Reuters reported.

The trademark battle spanned 15 years as the performer attempted to block the designer from registering the trademark and sought to stop her using it before dropping the move, Katie Perry claimed.

The clothing designer registered her brand name Katie Perry in 2008, a year after she started selling clothes under that name. It was the same year that Perry hit the big time with her song "I Kissed a Girl".

"Not only have I fought [for] myself, but I fought for small businesses in this country, many of them started by women, who can find themselves up against overseas entities who have much more financial power than we do," she said on her website and Instagram.

Judge Markovic ruled that the hitmaker infringed on the designer's trademark by promoting hoodies, sweatpants, T-shirts and other items on her social media, according to BBC News. However, she dismissed infringement claims around merchandise sales for her 2018 tour.

A ruling on damages will be made later this year.

Katy Perry is set to perform at King Charles III's coronation concert on May 7.

Representatives for Katy Perry didn't immediately respond to a request for comment from Insider made outside normal working hours.