Sarin Virgilio was a starship officer, specifically a Human from Masterra, who served in both the Rebel Alliance and the New Republic.
Virgilio was a member who fought for the Alliance to Restore the Republic. He served as third officer aboard a Corellian Gunship before the Battle of Endor. Virgilio's ship executed a rescue of the six surviving members of a Bothan Spynet team operating in the Outer Rim Territories. He was impressed by their bravery and became a staunch advocate for the Bothans and Councilor Borsk Fey'lya.
During the Thrawn crisis, Virgilio, having attained the rank of Captain, was in command of the EF76 Nebulon-B escort frigate named Quenfis. This ship was part of the Home Guard Fleet. Borsk Fey'lya dispatched him to apprehend Han Solo and his associates during the Katana fleet affair. During that same conflict, Fey'lya was tricked into revealing his true intentions, and Virgilio demonstrated his loyalty to the New Republic by siding with Solo and Rogue Squadron in the subsequent battle.
According to his entry in the Dark Force Rising Sourcebook (which was also republished in The Thrawn Trilogy Sourcebook), his ship was the one that recovered the Bothans who carried the Death Star II plans. This contradicts the events depicted in Star Wars: Shadows of the Empire.