Richard Sarwal, a longtime Oracle veteran, did not stay at VMware long, having joined the company in December 2007.
VMware CTO Stephen Herrod will begin overseeing research efforts effective immediately, according to VMware.
VMware is the top virtualization vendor, with 76.4 percent market share in 2007, followed by IBM with 9.8 percent, according to IDC.
Other vendors, including Microsoft, Oracle and Sun, have been pushing hard of late behind their own entries, creating an atmosphere of heightened competition despite VMware's significant lead.
The company recently fired its CEO and co-founder, Diane Greene, but Greene's husband and fellow co-founder, Mendel Rosenblum, remains there as chief scientist.
Oracle could not immediately be reached for comment Tuesday.