worth £3million.The singer claimed the ‘unendorsed’ white T-shirt with a photograph of her in a bra top may have damaged her image because fans could have thought it was genuine merchandise.
The Barbadian star and two Los Angeles-based associated companies claimed she is entitled to damages from Arcadia Group Brands Ltd, which operates Topshop, over the unauthorised use of her picture.
Topshop disputed her claim but Judge Mr Justice Birss ruled in her favour today after a hearing in London, but will decide on damages at a later date.
But he said the 'mere sale' of a T-shirt bearing the image of a famous person was not necessarily an act of 'passing off'.
He said a 'substantial number' of buyers were likely to have been deceived into buying the Rihanna T-shirt because of a 'false belief' that it had been authorised by the singer.
The judge said that was damaging to her 'goodwill' and represented a loss of control over her reputation in the 'fashion sphere'.
He said it was for the singer not Topshop to choose what garments the public thought were endorsed by her.
The judge did not make any assessment of damages in a written judgment published today.
The superstar's team asked the high street clothing chain run by billionaire Sir Phillip Green to stop selling them.
The legal threat came despite the What's My Name singer having dined with Sir Philip and music mogul Simon Cowell while on her Christmas break to Barbados in 2010.
The star, who last year signed a deal worth a rumoured £800,000 to design a range with High Street rival River Island, tweeted about the Boxing Day meal they had together, saying: 'Just had dinner w/ Simon Cowell Philip Green @ Sandy Lane! Great night!'
She has also spent time with Sir Philip's daughter Chloe while holidaying at the same time in the Caribbean two years ago.
It was even rumoured she might follow in the footsteps of Kate Moss and design a range for Topshop, but the two parties ended up in court.
A barrister at London's High Court claimed Rihanna's representatives had asked Topshop for products for the singer on '10 recent occasions', and said her 'shopping habits' were testament to the retailer's own considerable reputation.
Of those 10 occasions, six came after Rihanna launched proceedings against Topshop, said Geoffrey Hobbs QC.
Mr Hobbs said: 'It is not in dispute that Rihanna is a celebrity (but) the reputation of Topshop is also material to the allegation of misrepresentation.
'Rihanna's own shopping habits provide compelling evidence of Topshop's reputation in fashion wear. (There are) 10 recent occasions on which her representatives have contacted Topshop asking for products for her to wear.
'We note that six of these requests post-date this dispute,' the barrister said.
The T-shirt in question is printed with a snap of the star wearing a bra top, which she says was 'very similar' to images used on one of her album covers.
She claimed sales of the shirt amounted to 'passing off' and may have led to her reputation being tarnished with her fans, had they bought the garment thinking it was 'genuine' endorsed merchandise with 'an emotional connection to their heroine'.
Lawyers for Topshop maintained the retailer did nothing wrong, and accused the pop star of making an unjustifiable bid to establish a 'free standing image right' over use of her picture in the UK.
Mr Justice Birss, sitting at London's High Court, heard that Topshop bought a licence to use the image on the T-shirt from the photographer who took it, during the video shoot for Rihanna's single We Found Love which was filmed in Belfast and Bangor, Northern Ireland, in November 2011.
However the 25-year-old singer protested that they had short changed her and her fans when the T-shirt went on sale.
Martin Howe QC, for Rihanna, who is suing Topshop's owners, Arcadia Brands Limited under her real name, Robyn Rihanna Fenty, told the court: 'Rihanna is one of the world's most famous musical performing artists. She needs little introduction.
'Like most well known contemporary performing artists, she engages in merchandising, and like most such performing artists, it represents a significant part of her revenue stream.
'In 2012, Topshop sold a T-shirt displaying a clearly recognisable image of Rihanna taken when she was on a video shoot. She was wearing her makeup and hairdo for the video shoot, and very similar images of her appeared on her CD inlay (for the album Talk that Talk.)
'A substantial number of people buying, or even seeing, those T-shirts would think they are approved or somehow connected with Rihanna, when, in fact, they were not approved of or connected with her at all.'
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