A source told Us Weekly magazine: "They have been dating -- for months! They're exclusive, and it's very hush-hush."
The pair have not yet been photographed together, but the magazine reports that witnesses saw the 'Green Lantern' actor's motorcycle parked outside Charlize's house all morning one day last month, before Ryan eventually emerged from the property at 3pm and she left just minutes later.
Insiders believe the pair make a good couple because of their similar attitudes to work.
One source said: "They're both career-focused but not in a crazy way."
However, Charlize – who ended her nine-year relationship with Stuart Townsend last year – is not planning to be seen in public with Ryan any time soon.The source said: "She won't go to an event with him. That's not her style."
Meanwhile, Ryan recently found the time to have dinner with 26-year-old Scarlett at Little Dom's in Los Angeles.
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