El-Gatark was a region of space close to the border between the United Federation of Planets and the Cardassian Union.

El-Gatark was the site of a battle between the USS Valiant and a Cardassian battle cruiser in the early days of the Dominion War. (DS9: "Valiant")

The Star Trek Encyclopedia (4th ed., vol. 1, p. 230) located El-Gatark in Federation territory.
According to Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), El-Gatark was a star system in the Alpha Quadrant. The system's primary was a M-class star.