Denis Slowley has been a principal for the past 24 years, the last 12 of which at Bayfield High School.
The former principal of Wainuiomata College and Huntly College said he had reached a stage in his life where he was feeling increasingly compelled to try something different.
"I lost my wife four years ago to cancer and I lost my mother recently, as well.
"Lately, it has reminded me constantly how important family is. And now that I'm 63, it is time to dedicate more time to my family."
Mr Slowley said he also wanted more spare time to finish a doctorate on school leadership at the University of Otago, and indulge his passion for painting.
During his leadership, the school's aim had been to turn out pupils who were among the leaders of tomorrow and with the skills to face the challenges of an ever-changing world, Mr Slowley said. He believed his departure would not diminish that philosophy.
"I've loved my time at the school and I have lots of regrets about leaving," he said.
"But other people need to have a chance to be a principal.
"I think the school will do well under a new principal," Mr Slowley said.
Board of trustees chairman Jeff Clamp announced Mr Slowley's resignation with regret.
"Denis will leave with our sincere gratitude, and an excellent record of achievements, after almost 12 years of excellent service to both the school and the Dunedin education community.
"The board will shortly begin the search for a high-quality successor," he said.
