It gets a little more complicated unfortunately:

"At one time, type O negative blood was considered the universal blood donor type. This implied that anyone — regardless of blood type — could receive type O negative blood without risking a transfusion reaction. However, we now know even type O negative blood may have antibodies that cause serious reactions during a transfusion."

http://www.mayoclinic.org/tests-procedur...pe/faq-20058229