The Apollo-class was an early 24th century Starfleet vessel. The Apollo was still in use by the 2370's,
however has been almost completely phased out of service.
The actual design of the Apollo is unknown. In "Unification" the T'Pau along with three other Vulcan
ships are listed as Apollo-class by the Star Trek: Encyclopedia.
The class name comes from Greek mythology and the Apollo space program which brought Humans to the moon.