The Irish singer, who has just turned 45, and her boyfriend have applied for a marriage license in Las Vegas.
The couple applied for and received a marriage license Wednesday night.
O'Connor also posted photos on her website showing her and fiancé Barry Herridge en route from Dublin to Sin City for what she called 'my absolute dream wedding ceremony'.
However, the couple are keeping the location of the ceremony, which was expected to take place on Thursday, a secret.
The Nothing Compares 2 U singer split from longtime friend and collaborator Steve Cooney in April.