The singer and "Saturday Night Live" comedian confirmed their engagement in June, just a few weeks after they started dating.
A source tells CNN they're now calling off the wedding.
The pair met while Grande was hosting "SNL" in 2014.
They made things official after she broke up with late rapper Mac Miller.
Davidson and Grande recently bought a home together. Grande named a song after him on her latest album.
A Grande source told People magazine that their relationship "was way too much too soon" and that the breakup is "not shocking to anyone."