Itamish III was the inhabited third planet in its star system.
In the 2360s, Benjamin Sisko, his wife Jennifer, and their son Jake once took a camping trip to Itamish III, where Jennifer taught Jake how to water ski. (DS9: "The Jem'Hadar")
Background information Edit
This planet was only mentioned in dialogue.
"ih-TAH-mish" was the pronunciation for this planet's name from the script pronunciation guide. 
StarTrek.com described Itamish as a Class M planet orbiting the star Itamish.
The Star Trek Encyclopedia (4th ed., vol. 1, p. 379) located Itamish III in the Itamish system.