Sector 5501 was a region of space.
In 2369, this sector was named on the chart "Sector Ipai Relay Log - Relay Message Flow 1293" in Relay Station 47 Ops. The USS K'Marco was in this sector around the same time that the USS Enterprise-D visited Relay Station 47. (TNG: "Aquiel", production art)
This sector was only mentioned in writing.