The Argelius sector was a region of space.
In October 2151, the Argelius sector was visited by Enterprise NX-01. When Captain Archer told Sub-Commander T'Pol that a Vulcan ship was scheduled to arrive there in two days and then take her back to her homeworld of Vulcan, T'Pol told him she wouldn't have time to finish her scans of the sector. Consequently, she planned to ask Ensign Mayweather to complete them. (ENT: "Shadows of P'Jem")