Mr McGowan, 55, held a snap press conference on Monday where he confirmed his intention to step down as premier and the member for Rockingham.
"Today I'm announcing I will be stepping down as premier and as member for Rockingham," he told reporters.
McGowan said he was "tired, extremely tired, in fact, I am exhausted".
"This job is like no other, after seven elections across nearly three decades, now is the right time to step away from the job that I have loved.
"This week will be my final week. It is not a decision I have taken lightly, I've been considering it for quite a while.
But I needed to hand down a state budget before a made a final decision."
The former Navy lawyer, who shepherded WA through the COVID-19 pandemic, led Labor to crushing election victories in 2017 and 2021, the latter securing his party the biggest parliamentary majority in the state's history.
He had previously insisted he would serve out the remainder of his second term as premier before considering his future.
He made the announcement flanked by members of his ministry.
AAP with The Project.
