(Played by William Windom)
Commander of the U.S.S. Constellation. In 2267, when his ship was attacked by a stray, extragalactic "planet killer" weapon, Commodore Decker evacuated his crew to the third planet in the L-374 system while he stayed aboard. But then his crew died when the planet killer destroyed the entire system. Gripped by grief and guilt, Decker later commandeered a shuttlecraft from the U.S.S. Enterprise for a suicide mission to destroy the machine. He died during the unsuccessful attempt, but his actions paved the way for the Enterprise to finish what he started, to ensure the planet killer's demise.
His son Willard Decker is slated to be the captain of the refit U.S.S. Enterprise in 2270 until the V'Ger crisis intervenes.