TMZ said Davidson, 28, has been filming a movie in Australia, while Kardashian, 41, is working and raising her four young children in Los Angeles.
Kardashian also is in the midst of a divorce from rapper Kanye West.
"They amicably split this week," one insider told UsMagazine.com of Kardashian and Davidson.
The still have "a lot of love and respect for each other," another source told E!, but they found that the distance and their demanding schedules "made it really difficult to maintain a relationship."
The pair started dating in October after Kardashian guest hosted Saturday Night Live, the sketch comedy show for which Davidson was a cast member at the time.
They made headlines when they walked the red carpets at high-profile events such as the White House Correspondents' Dinner in April and the Met Gala in New York City, and shared on social media photos from their various luxurious vacations.
Davidson recently quit SNL to pursue opportunities in film and standup comedy.