Caleb IV was the inhabited fourth planet in its system and home to a Federation outpost in the 23rd century.
In the 23rd century, the planet was the site of the Battle of Caleb IV. Caleb IV was attacked by two Klingon divisions led by Kang and Kor. Aboard the D5 class cruiser IKS Klothos, Kor outmaneuvered the defending Federation forces by attacking with an initial feint, and then returning with his full force, catching the Federation in the midst of their repair work.
In 2375, during a similar attack on a Dominion base at Trelka V, Kor believed that he was back at Caleb IV. (DS9: "Once More Unto the Breach")
This planet was only mentioned in dialogue.
"KAY-leb" was the pronunciation for this planet's name from the script pronunciation guide.