Media reports had said students at Brown University, in Providence, Rhode Island, had teased her about her role as Hermione in the Harry Potter films.
But in a statement on her website, Miss Watson, 21, said: "I have never been bullied in my life."
She said she did not know what she wanted to do after September, but would focus on acting for the time being.
She had enrolled at Brown in September 2009, initially to study literature.
Reports had alleged that students said "10 points to Gryffindor" - a reference to a house at Hogwarts, the school for wizards in the Harry Potter films - when Miss Watson correctly answered a question in class.
Miss Watson said: "I felt the need to let you all know the reason I took a semester off from Brown had nothing to do with bullying as the media have been suggesting recently.Continue reading the main story
Please don't try and speculate about what I might do in September - no-one can possibly know because I don't even know yet!”End Quote Emma Watson Actress "I have never been bullied in my life and certainly never at Brown. This '10 points to Gryffindor' incident never even happened.
"I feel the need to say this because accusing Brown students of something as serious as bullying and this causing me to leave seems beyond unfair."
Last month she announced she was taking time out of study to focus on her film career.
Although her spokeswoman said last week that Miss Watson would transfer to another university in autumn, Miss Watson's statement said: "Please don't try and speculate about what I might do in September - no-one can possibly know because I don't even know yet!
"Like my other fellow Brown students I am trying to figure out my third year and whether or not I will spend it abroad (this is common)."
In the frequently asked questions section of her website, the first question is "why did you chose Brown University over a British one?"
Her undated answer is: "I was seriously torn as to whether to stay in the UK or go to the States as let's face it the UK has some of the best universities in the world. But, ultimately, I loved the course at Brown and really liked the idea of experiencing a different country and culture - and I must say I've never been happier, I absolutely love Brown."
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