The ACT's longest serving chief minister, Jon Stanhope, is stepping down from the top job.

Mr Stanhope has served as chief minister for nearly a decade and last month celebrated his 60th birthday.

He says he will be leaving the Legislative Assembly in about a week when a new chief minister is chosen.

"This is a decision that I've come to only recently... it's clear to me that this is the right time. It's the right time for new leadership in the Labor Party and for the people of Canberra," he said.

Mr Stanhope says he expects Treasurer Katy Gallagher will take over as chief minister.

"The Labor caucus will meet on Friday to select who it will put forward for vote in the Assembly to be the new chief minister," he said.

"I propose at that meeting to nominate Katy Gallagher for chief minister. I believe Katy Gallagher will be elected as chief minister. It is the right time for Katy," he said.

If elected, Ms Gallagher will be the third female to head an ACT government, following in the footsteps of Rosemary Follett and Kate Carnell.

Education Minister Andrew Barr is expected to be named her deputy.

"As I move, there will be no void because it will be filled immediately and fully by a wonderful new leader and chief minister in Katy Gallagher," Mr Stanhope said.

Mr Stanhope says it is the right time for him to resign, both for himself personally and for the Labor Party.

"My driving commitment during my 10 years as chief minister has been to imbed the core principles of social justice, freedom from discrimination, human rights, equality of opportunity and the rule of law, ever more firmly into our community," he said.

He says his most satisfying achievement has been the way he and his government have implemented those core social principles.

"I'm thinking of the ACT Bill of Rights that was the first in the country, the first prison built to human rights principles, the removal of all legislative discrimination against gays and lesbians and the introduction of civil partnerships ... the repeal of legislation that made abortion illegal in the ACT," he said.

Mr Stanhope says he does not yet know what he will do next.

He says he is "fit as a fiddle" and looking forward to the next stage of his life.

"I do want another career, at this stage I have no idea what it might be or could be in a context of such as large, momentous decision in life, not knowing what the future may hold," he said.

"I have no job offers, indeed I have not even raised the possibility. I'm hoping the future will look after me and itself."

'Wonderful leader'

Katy Gallagher says Mr Stanhope is a dedicated, hard working Canberran.

"I don't think anyone can say he hasn't been a wonderful leader or a strong leader, even if you disagree with him. He's always there prepared to take up the challenge," she said.

"He's certainly not arrogant, but he is an introvert. He wasn't a natural communicator when he first came into politics but he has developed that over his career in politics.

"He's intense but he a very compassionate and understanding man, and one of the most intuitive men I've ever me, he doesn't miss anything."

She says it has been a pleasure working with Mr Stanhope.

"He's the best boss I've ever worked for in terms of his encouragement of me," she said.

"He's mentored me. He was very good when I had two babies during one electoral term. He's been my boss for 10 years and that has a huge impact.

"He's been very good about mentoring and ensuring other people are coming up to take-over."

Ms Gallagher says she is ready to take on the role of chief minister, but she says she is not taking anything for granted.

"Jon's been mentoring me and preparing me. I would always work hard in the interests of the community where I was born and where I'm bringing up my family," she said.

"But that's a matter which will be dealt with on Friday."

Former ACT treasurer Ted Quinlan says one of Mr Stanhope's legacies will be standing up for what he believed in, even when it is against popular opinion.

"We've seen political leaders in the past and sometimes we see them these days who are just driven by polls and by interpretation of public opinion and not prepared to lead public opinion," he said.

"Jon I think will be remembered in history as a genuine public leader."

Former ACT chief minister Kate Carnell says she is not surprised by Mr Stanhope's decision.

"Jon has been in the job for 10 years now and that's a very long time in the top job. I was there for nearly six and I understand just how tough that is," she said.

"Jon has been a good chief minister for Canberra. Obviously there's things that I would have done differently but I think you'd have to say he's been a good representative of the ACT."

Ms Carnell says Ms Gallagher has shown she has the capacity to take on the top job.

"Katy Gallagher has been given just over 12 months to get into the seat, when I resigned I also gave my deputy 12 months, to establish themselves as a real leader. So I wish Katy all the best," she said.

Political career

Mr Stanhope was elected as a Member for Ginninderra for the Labor Party in 1998, taking over the party's leadership.

After the 2001 election he became chief minister, forming a minority Labor government.

He made national headlines in 2003 when he rescued a helicopter pilot who had crashed into a dam.

But he faced one of his greatest challenges later that year when deadly bushfires swept through Canberra destroying hundreds of homes.

Mr Stanhope formed the ACT's first majority government at the 2004 election, after Labor won nine of the Legislative Assembly's 17 seats.

He went on to introduced the Human Rights Act in 2004, making the ACT the first jurisdiction in Australia to do so.

At the 2008 election Labor lost two seats and formed a minority government with the Greens.

The next ACT election is due to be held in October next year.