"Karl has made a very significant contribution to Tauranga Art Gallery, growing it's visitation and furthering its reputation both locally and nationally," Tauranga Art Gallery Trust chair Peter Anderson said.
"We will miss his expertise and passion, but his new role is a wonderful opportunity and we wish him the very best."
Tauranga Art Gallery, as a Council Controlled Organisation, has a close working relationship with Tauranga City Council.
Deputy mayor and councillor Kelvin Clout has worked with Chitham during his tenure at the gallery.
"It's been a pleasure working with Karl, he has ensured a close-working relationship between the gallery and TCC," Clout said.
"We are also very pleased with the great results he and the team produced since he joined the gallery in July 2015."
Chitham will be leaving the gallery with a full complement of staff and has already planned activities for 2019, including a partnership with the 2019 Tauranga Arts Festival, festival director Jo Bond confirmed.
"Karl and I have already begun work on a great collaboration for next year," Bond said.
"I will miss working with him but look forward to continuing our relationship with the gallery".
Chitham's vision, drive and dedication to creating exceptional art experiences has not gone unnoticed by his new employers.
Hutt City Council general manager of city and community services Matt Reid was impressed by Chitham's leadership achievements and vision for the future.
"Karl is keen to ensure the arts can positively influence everyone's lives and wants to create accessible and high quality museum, arts and cultural experiences for everyone," he said.
Recruitment for a new Tauranga Art Gallery Director will begin in October.