Sarel Pretorius will leave the Dragons at the end of the season after agreeing to join Guinness PRO14 rivals Southern Kings.
The 33-year-old scrum-half has made 70 appearances and scored 15 tries since joining the Welsh region from the Cheetahs in 2015 but will return to his native South Africa for the 2018/19 campaign.
"I made up my mind to sign a two-year deal with the Kings when we were out there a month ago," he said, referring to the Dragons' 45-13 loss in Port Elizabeth on March 2.
"Seeing what I missed out there and also at this time in my career, it's time for another new challenge.
"I've had a great time at the Dragons, made a lot of good friends and good memories, so I want to say thank you to all the supporters who have stayed with us through thick and thin."
Dragons head coach Bernard Jackman added: "He is the ultimate professional and has proven to be one of the most dangerous running scrum halves in the PRO14 just like he was in Super Rugby.
"While we are disappointed to see him leave we understand why it makes sense for him and his family to move back to South Africa and we look forward to catching up with him when we play the Kings over the next two seasons."