Galen was an alias assumed by Captain Jean-Luc Picard in 2370 while investigating the raiding of Nafir on Dessica II. Picard adopted this alias when his investigation drew the attention of the thieves, led by Arctus Baran.
As Galen, Picard apprised the ancient Romulan artifacts raided from archaeological sites in the Taugan sector. He claimed that he was a smuggler who for years had been smuggling artifacts from Federation sites. During those years, he had developed a familiarity with certain Starfleet officers, including William T. Riker. (TNG: "Gambit, Part I", "Gambit, Part II")