The Federal Government has announced two new High Court justices.

Two current Federal Court Judges - Jacqueline Gleeson and Simon Steward - will replace outgoing Justices Virginia Bell and Geoffrey Nettle.

“They are outstanding judges, they have been outstanding members of the legal and broader Australian community,” Attorney-General Christian Porter said.

Justice Gleeson's father, Murray Gleeson, was also a High Court justice.

“It's not really possible to appoint her honour Justice Gleeson without noting she is the oldest daughter of former High Court chief justice Murray Gleeson,” Mr Porter said.

“I'm told that's a first in common law countries.”

The two outgoing High Court justices are approaching the mandatory retirement age of 70.

Justice Nettle will be by Justice Steward in early December.

Justice Bell's birthday in March next year. The new Justice Gleeson will take up her High Court seat at the start of that month.

Justice Steward has focused primarily on tax law throughout his career, and worked alongside current Justice Michelle Gordon when both were at the bar.

Justice Gleeson has a much higher public profile, being briefed on Canberra bushfire litigation from over 100 complainants, and representing Alan Jones at the Australian Broadcasting Authority's (ABA) cash-for-comment inquiry.

Prime Minister Scott Morrison has thanked the retiring justices for their work.

“Every justice appointed to the High Court carries a significant burden to uphold the laws of our land,” he said.

“I congratulate Justices Steward and Gleeson and I wish them all the best.”