Paul Winfield portrayed Captain Clark Terrell in Star Trek II: The Wrath of Khan. He then appeared on ST:TNG in the role of Dathon in the classic "Darmok" episode.

Biography from Leonard Maltin's "Movie Encyclopedia" (courtesy of IMDb.com):

This imposing black actor first came to the attention of TV audiences opposite Diahann Carroll on the sitcom "Julia" from 1968 to 1971, and he's done some of his best work on the small screen, especially as civil-rights activist Dr. Martin Luther King, Jr., in "King," a 1978 miniseries. Winfield's feature-film success has been limited to a few choice roles, notably the dignified sharecropper in "Sounder" (1972, for which he received a Best Actor Oscar nomination), but he's had plenty of movie work over the last two decades without falling into the blaxploitation quagmire. He debuted in "The Lost Man" (1969), and was visible in "R.P.M" (1970), "Conrack," "Huckleberry Finn" (both 1974), "The Greatest" (1977), "Carbon Copy" (1981), "Star Trek II: The Wrath of Khan" (1982), "Blue City" (1986), "The Serpent and the Rainbow" (1988), and "James Baldwin: The Price of the Ticket" (1989). He had a particularly thankless time going up against murderous cyborg Arnold Schwarzenegger in "The Terminator" (1984). Winfield's outstanding performance as an animal trainer trying to "break" a dog programmed to attack blacks in Samuel Fuller's "White Dog" (1982) was unseen for many years because Paramount shelved the movie, embarrassed by its subject matter. He had a good supporting role as a judge in the courtroom drama "Presumed Innocent" (1990), but his best parts in the past 15 years have mainly been on stage or in TV dramas, including the miniseries "Roots: The Next Generation" (1979), "Alex Haley's Queen" (1993), and "Scarlett" (1994).