The Wallenberg-class starship was a large type of transport/tug active in the late 24th century. They were used by the Federation Starfleet, and were described as warp-capable ferries.
A large number of these tugs were constructed at Utopia Planitia Fleet Yards at Mars after the Federation decided to assemble a rescue armada in order to relocate nine hundred million Romulans from the impending supernova of the Romulan sun. On April 5, 2385, a fleet of synth ships attacked the yards, destroying the armada.
None of these tugs carried a formal registry, however, at least one ship carried a mark of "180/27". (PIC: "Remembrance", "Maps and Legends")
In the 2380s, these transports were used by the Federation for evacuating Romulans from the Romulan system. (PIC: "Absolute Candor")
While the Wallenberg-class name wasn't directly linked to this design in an episode, the name for this class was confirmed by Michael Chabon. 
This class was named after Swedish diplomat Raoul Wallenberg, who saved thousands of Jewish people from the Holocaust in Budapest, Hungary during World War II.