That includes navigating the Covid-19 pandemic, securing significant funding from the Government for infrastructure projects, and introducing the Ambassador Programme to improve city safety, among other achievements.
Napier Mayor Kirsten Wise thanked her for her leadership.
"We are all very sad to see Steph go however are thankful for her leadership in her time with us and respect her desire to return to the sector she served in for many years."
The council stated the role of acting chief executive would be announced in "due course".
In 2020, former Napier City Council chief executive Wayne Jack resigned from the role after seven years in the job.