Starbase Icarus was a Federation starbase.
When Admiral Charlie Whatley ordered the evacuation of all Starfleet personnel from Deep Space 9 in 2372, they were to be taken to the starbase by the USS New York. The USS Defiant and her crew were to rendezvous at Starbase Icarus soon after. (DS9 novel: The 34th Rule)
Sivadeki was once assigned to Starbase Icarus. (ST - Typhon Pact novel: Rough Beasts of Empire)