The USS Delphi was a Federation starship in service in the late 23rd century.
In the alternate 2270s in which the Federation was at war with the Gorn Hegemony, the Delphi was assigned to the frontier fleet that was tasked with attempting to stop the Gorn invasion of the Prellant system. Serving aboard the Delphi at this time was former USS Enterprise crewmember, Joe Tormolen. (TOS - The Janus Gate novel: Present Tense)