Constitutional law expert Justin Gleeson SC has become Australia's 10th solicitor-general.

The barrister, who has been acting solicitor-general for four months, has been appointed immediately for a five-year term.

Attorney-General Mark Dreyfus said Mr Gleeson replaces Stephen Gageler SC who was appointed as a Justice of the High Court of Australia last year.

"Mr Gleeson is a respected member of the New South Wales Bar and his expertise as an advocate in complex matters involving Australian private and public law and constitutional law will serve him well in his role," Mr Dreyfus said in a statement.

Mr Gleeson was admitted as a barrister of the High Court of Australia in 1989 and was appointed senior counsel in 2000.