Senate President Scott Ryan will resign at the next election after 14 years in parliament.
The coalition senator from Victoria announced his decision on Twitter on Sunday.
"Today I announced to my annual BBQ for Liberal members and supporters that this will be my last term in parliament," he said.
"It has been a privilege to represent the people of Victoria for over a decade, to serve as a minister and currently as President of the Senate, only the second Victorian to do so."
He served in various assistant ministry roles and as vocational education minister under the Turnbull government before being appointed senate president in 2017.
As Senate president, he oversaw and regulated the upper house.
Senator Ryan said he was unwilling to commit to continuing until 2028 and wanted to provide sufficient notice to the Liberal Party.
Australian Associated Press