Grand Admiral William Smillie was a Human Starfleet officer who served as the Commander-in-Chief of Starfleet in the early 2290s.
In 2289, Admiral Smillie signed the orders that assigned Hikaru Sulu to the first officer position on the USS Excelsior under Lawrence Styles. (ST novel: Excelsior: Forged in Fire)
In 2293, Admiral Smillie held a briefing at Starfleet Headquarters to respond to the situation with the Klingon Empire following the destruction of Praxis. Following the peace overtures that were being made by Captain Spock and Chancellor Gorkon, he ordered Captain James T. Kirk and the crew of the USS Enterprise-A to rendezvous with Gorkon and escort him to Earth.
Along with Colonel Worf, he revealed the true identity of the Federation President Ra-ghoratreii's
would-be assassin: Colonel Patrick West. (TOS movie: Star Trek VI: The Undiscovered Country)
Some months later, Smillie presided over the memorial service for Captain Kirk which was held in the grounds of Starfleet Academy. (TOS - Crucible novel: The Fire and the Rose)
In an alternate timeline in which Spock was killed at the age of seven in 2237, Smillie was killed when the Cetacean Probe ravaged Earth in 2286. (TOS - Myriad Universes novel: The Chimes at Midnight)