Looks like Rihanna's really getting into the spirit of Fashion Week - heck, over the weekend, she shopped at three ultra-fashionable boutiques in one day!

We caught the singing sensation stepping out for a little shopping on Saturday afternoon. We just didn't count on her doing quite so much shopping - she ended up spending the whole afternoon perusing the wares at Louis Vuitton, Gaultier, and Ungaro!

And believe it or not, even all that shopping couldn't quench RiRi's appetite for couture - later that night, we spotted her making a big appearance at the big Fendi opening!

Whew - Rihanna's gonna need a vacation to unwind after her vacation!