Ktaris, also known as Ktaria and Ktar, was an inhabited class M planet located in the Ktarian star system in the the galaxy's Alpha Quadrant Ktaris was the homeworld of the Ktarian civilization. (ST novels: Articles of the Federation, Allegiance in Exile, VOY episode: "The Voyager Conspiracy")
In the year 2270, the Federation made first contact with the Ktarians when the USS Enterprise visited them during their exploratory tour of a sector in the Alpha Quadrant surrounding Starbase 25. (TOS novel: Allegiance in Exile)
In the 2370s decade, Libby Webber moved from Earth to Ktar to further her studies as a musician using the Ktarian lal-shak. While working as agent for Starfleet Intelligence's Covert Operations, Webber helped uncover a plot to attack the Federation. Initially believed to be a Ktarian scheme, Webber cleared the Ktarians' and identified another alien race as the planners. (VOY novel: Homecoming)
On stardate 53329 (2376), USS Voyager crewmember Naomi Wildman programmed a model of her father's homeworld Ktaris as an entry in the first Annual Voyager Science Fair. Naomi showed Captain Kathryn Janeway the storm system of the planet, particularly a hurricane hitting the Arpasian Range. (VOY episode: "Child's Play")
Around April 5th, 2382, the pilot Greskrendtregk and his daughter Naomi traveled to Ktaria in the runabout USS Coleman. It was on the "Beta" route devised by Seven of Nine and Tom Paris, which led to a region that contained planets viable for settlement by the Arehaz refugees. Greskrendtregk chose the Beta route because he was familiar with the area.
Greskrendtregk and Naomi spent time with his family on Ktaria. She met two of her cousins and her paternal grandmother, and fell in love with the jungles and the Ktarian wildlife. After Naomi returned to Earth to bid goodbye to Seven, she told her she would stay on Ktaria. Her mother, Lieutenant Commander Samantha Wildman, received a new posting on Ktaria, so that the Wildman family could live together on the Ktarian homeworld. (VOY novel: Atonement)
From 2409 onwards, one task performed by duty officers aboard Starfleet ships was to verify diplomatic correspondence from a Federation ministry with the Ktarian homeworld. (STO - "Klingon War" mission: "Diplomatic Orders", duty officer assignment: "Review Diplomatic Correspondence")