Dennis Sweeney was a male Human Starfleet security officer during the 2270s.
In 2275, Sweeney served aboard the USS Enterprise under Pavel Chekov in the security division. During this time, Sweeney was forced to busy himself to avoid watching an argument between Chekov and efficiency auditor Aaron Kelly. Later that year, Sweeney was killed by the Orion spy who assumed the identity of Lindsey Purviance. (TOS novel: Death Count)