According to comScore, that's British tabloid The Daily Mail, beating out presumptive leader The New York Times with a December user score of 45.3 million people to 44.8 million, respectively.
But the Times claims the Mail total unfairly added in a personal financial site. "The Daily Mail is not in our competitive set," sniffs a spokeswoman.
Whatever. Still, a good discussion of the Mail's digital strategy -- moving slowly toward monetizing international traffic -- here.