The long-serving Howells originally joined City's managerial team during the 2007 close season as coach and became assistant-manager in October 2008.
In October 2012 he was named head coach after Adie Britton became director of football development.
He leaves after a poor run of two wins in seventeen games in the league.
The Bath City Board of Directors have thanked Howells for his dedication and hard work over the last eight years and have wished him well for the future.