Kim, 28, began dating the 24-year-old NFL star in April 2007.
According to a source close to the former couple, the split was a "mutual decision."
"Nobody cheated. This was just a case of conflicting schedules and their lives going in different directions," the source told Access.
In June, Kim hit her blog to dispel rumors the two were set to walk down the aisle.
"I am not engaged!!!" she wrote at the time. "I don't know where all this comes from!… Don't worry guys, you will be the first to know if and when I get engaged!!… Well after I tell my family, of course!"
"We met at the  ESPY Awards," Kim previously told AccessHollywood.com of her initial encounter with Reggie. "My stepdad, Bruce, and I were walking to our seats and Matt called my name. When I went over, he was sitting with Reggie…. Matt introduced me to the love of my life and we will always be grateful."
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