Ambulance Victoria chief executive Jane Miller has resigned amid mounting pressure from ongoing industrial disputes and increasing work demands.
In a statement, the agency said the resignation was effective immediately.
"Jane has seen the organisation through some significant challenges, including leading the post-pandemic recovery, and helping chart a course for ongoing cultural reform and improvement," board chair Shelly Park said.
"She has been instrumental in the development of AV's Strategic Plan 2023 – 2028: Transforming for Better and has been an enthusiastic leader in supporting the critical role of our paramedics and first responders."
Former emergency management commissioner Andrew Crisp has been appointed as interim chief executive for a six-month period.
It comes just weeks after Victorian paramedics passed a vote of no-confidence in leadership.
"The workforce voted no confidence in the AV Executive because new leadership is desperately needed to return Ambulance Victoria to the emergency service it is meant to be," Victorian Ambulance Union general secretary Danny Hill said in a statement.
"AV has been heading in the opposite direction for the past two years.
"The work involved in fixing the service will be massive, but this is the first step in the right direction.
"We welcome the appointment of Andrew Crisp, who has decades of emergency service experience.
"However, there is no time to waste in addressing the concerns that our members have been raising for several years and resolving our 18-month dispute."