The NSW State Emergency Services Commissioner Mark Smethurst has resigned following allegations of misconduct.
Police Minister Troy Grant said he accepted Mr Smethurst's resignation on Friday afternoon.
"I have no tolerance for misconduct and allegations will always be taken seriously no matter who they relate to," Mr Grant said in a statement.
"Appropriate measures have been put in place to support those affected by this matter."
The minister did not comment on the nature of the misconduct allegations.
It's understood the complaints were made recently and an investigation was launched not long before Mr Smethurst stepped down.
Mr Smethurst was appointed NSW SES Commissioner in February 2017.
“This appointment will ensure sound leadership of the NSW SES and the further development of the organisation to help meet the challenges faced in times of crisis," Mr Grant said at the time of Mr Smethurst's appointment.
Before joining the SES, Mr Smethurst was a brigadier in the Australian Defence Force. He spent most of his 35-year career in the ADF as a special forces officer in the Special Air Service Regiment.
Mr Grant appointed NSW Police Force Assistant Commissioner Kyle Stewart as interim SES commissioner until the position is formally advertised.
The new appointment will be made by the next police minister.
Mr Grant said Mr Stewart has had a "long and distinguished career" with the police, and also has extensive experience in emergency service management.
The police minister said the thousands of dedicated SES volunteers would be in good hands with Mr Stewart.
"I’m confident that their important work will continue under the leadership of Acting Commissioner Stewart," he said.
A NSW SES spokesman said he had no further information beyond the minister's statement.