From Halopedia, the Halo wiki
New Constantinople is a human colony world, governed by the Unified Earth Government. In early 2537, a major battle between the United Nations Space Command and the Covenant occurred in the planet's system. Vice Admiral Danforth Whitcomb distinguished himself in this engagement, as did the Spartan-IIIs from Alpha Company.
The planet is named after the capital city of the former Byzantine Empire, Constantinople.