The SS Carlos was supposedly a colonial ship in service during the 23rd century.
In 2259, Doctor Aspen reported the Carlos to be one of three colonial ships, along with the SS Raccoona and the SS Tiptree, that had lost power on the edge of Federation space. When the USS Enterprise arrived to render assistance, it found debris identified as belonging to the Carlos and the Raccoona. It later emerged that the stranded colonial ships were a fabrication of the pirate Captain Angel, who had taken Aspen's identity for a plot to capture the Enterprise. (SNW: "The Serene Squall")
The name of this ship was only referenced on the Enterprise viewscreen.