The Defender-class was a type of Federation starship in use in the 23rd century. The class was described as having a primary hull three times as large and four engine nacelles each twice as long as a Constitution-class starship, and the engineering hull was described as being a mile long and a quarter mile in diameter. The class was also said to carry more power and armament than any three starships combined, and had been built large to carry a lot of people on very long hauls. (TOS novels: The Wounded Sky, My Enemy, My Ally)