The company gave no reason for his departure, but said he would stay until the end of August to help with the transition.
St Barbara said a “structured succession process” to replace Lehany was advanced and it expected to make an early appointment of a replacement.
“An early priority of the replacement will be to consolidate the operational excellence of the Leonora operations and assess and resolve the strategic options for the future of the Pacific operations,” St Barbara said.
Lehany oversaw the disastrous $A556 million takeover of Allied Gold in late 2012.
Since completing the takeover in September 2012, St Barbara shares have slumped by more than 91%, though the gold price also fell heavily over that period.
Allied’s Simberi mine in Papua New Guinea and Gold Ridge mine in the Solomon Islands have weighed heavily on St Barbara due to continued underperformance, and more recently, a suspension at Gold Ridge due to flooding.
Last month Moody’s Investors Service downgraded the corporate family rating and senior secured rating of St Barbara to Caa1 from B3, with a negative outlook.
It said it did not forecast Gold Ridge to restart production before the end of the year.
Lehany, a mining engineer, was appointed MD and CEO of St Barbara in March 2009, taking over from Edward Eshuys.
He joined the Melbourne-based miner from Newcrest Mining, where he had been executive general manager operations.
St Barbara shares were unchanged at 14c.