Wendell Greer was an alias of a male Human bureaucrat in the 24th century United Federation of Planets. By 2375, Greer was the Assistant Director of the Federation Department of Cartography. Greer started his career in 2360.
In 2375, the alias was taken by Luther Sloan in order to attend a joint Federation-Romulan conference about the Dominion War on Romulus. There, William Ross and Koval also knew Greer's true identity as part of the Section 31 plot. As Greer, he talked to others at the conference, attended talks, and talked to Julian Bashir discreetly. Greer was "captured" by Koval, who claimed to know his true identity (because he himself was part of the plot) and exposed it to the Romulan Continuing Committee. At that point, the alias was known to be false in front of the Romulans. Through an incident, Sloan (and Greer) were thought to have been killed on the floor of the Committee. (DS9: "Inter Arma Enim Silent Leges")