The 34-year-old actor, who played Loki in "Avengers: Age of Ultron", was seen with Olsen, 26, at The Wolseley restaurant in London, reported Ace Showbiz.
Their appearance together in public fuelled dating rumours which have been swirling since May.
The two were photographed sitting side by side in a cab. Olsen looked chic in a black outfit while she put her hair in a ponytail. Meanwhile, Hiddleston looked relaxed in a white T-shirt topped with black blazer.
Earlier in the week, Hiddleston and Olsen were spotted getting cozy while walking down the street together in Oxford on July 21.
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Two days later, they took a taxi together to attend Bradley Cooper's West End production of "The Elephant Man".
Both Olsen and Hiddleston have been slated to star in Hank Williams biopic "I Saw the Light".
Olsen has been tapped to portray the late musician's wife Audrey Mae with Hiddleston playing the Alabama country music crooner. The biopic's release date is yet to be confirmed.