The pop superstar made an appearance at the catwalk show for the collection on Saturday night (February 16) at the capital's Old Sorting Office, clad in one of her self-designed black dresses for the store.
The range includes crop tops, bold-coloured and monochrome-striped separates, printed trousers and a strappy black gown with a risqué thigh-high split.
The Bajan singer previously explained her inspiration for her fashion line in a behind-the-scenes video, saying: "The theme throughout the entire collection was easy, laid-back chick, flirty... not very conservative, but I think everyone can wear this line.
"It's not too costumey, it's not too sexy - it's just very simple, very laid-back."
Rihanna's debut collection for River Island will go on sale instore and online on March 5.
Watch Rihanna talk about the range below:
Photo gallery - the Rihanna for River Island collection:
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