Captain James Kirk’s middle initial is T, making his full name James Tiberius Kirk.
Kirk is the commanding officer of the USS Enterprise in Star Trek: The Original Series. William Shatner played him in the original television series, which ran from 1966 to 1969, and later returned for the animated series and seven feature films. The initial appears in dialogue, official character listings, and the character’s full name.
Tiberius was not chosen at random. Gene Roddenberry had previously used the name for a leading character in his earlier television series, The Lieutenant. It became part of Kirk’s established identity in Star Trek, although the original series usually calls him “Captain Kirk” or “Jim.”
The surname and initial can be confused with other Kirk family names. His brother is George Samuel Kirk, usually called Sam, while James’s full name is James Tiberius Kirk. Chris Pine later portrayed an alternate-timeline version of Kirk in the 2009 film series, but that version also uses the middle name Tiberius.