Newcastle Reform's Rabbi Barbara Borts has resigned because she "wants to move on".
Rabbi Borts has given six months' notice to the 150-member congregation she has served on a part-time basis since 2008.
"I have had a good time here," she said. "They are a great bunch of people. If they need help I will continue to help them. I am not leaving them in the lurch."
The native Californian, who was ordained in 1981, is also a religious theology lecturer at Durham University.
She wanted "more time to finish my PhD on music and identity in the Reform Movement". She is also training to be a chazan.
Chairman Bill Fleming told congegants that the shul was exploring options to maintain "some kind of rabbinical leadership.
"We would very much like to remain in touch with Rabbi Borts."