Dame Lowell Goddard has resigned as head of the independent inquiry into child sexual abuse.
Dame Lowell, 67, a New Zealand high court judge, was appointed to lead the inquiry following the resignation of two previous chairwomen.
Home Secretary Amber Rudd said: "I can confirm that Dame Lowell Goddard wrote to me today to offer her resignation as chair of the independent inquiry into child sexual abuse and I have accepted.
"I want to assure everyone with an interest in the inquiry, particularly victims and survivors, that the work of the inquiry will continue without delay and a new chair will be appointed.
"I would like to thank Dame Lowell Goddard for the contribution she has made in setting up the inquiry so that it may continue to go about its vital work."
The inquiry was set up in 2014 amid claims of an establishment cover-up following allegations that a paedophile ring operated in Westminster in the 1980s.
Dame Lowell, who was appointed in April 2015, quit on Thursday afternoon in a resignation letter that was sent to Ms Rudd.
She wrote: "I regret to advise that I am offering my resign as chair of the independent inquiry into child sexual abuse, with immediate effect. I trust you will accept this decision."
In accepting Dame Lowell's resignation, Ms Rudd wrote: "I know that this will have been a difficult decision for you to make, and something you will have carefully considered. I was sorry to receive your letter, but I accept your decision."
Ms Rudd described the inquiry as the "most ambitious public inquiry ever established in England and Wales" and praised Dame Lowell for having helped it to make progress.
Ms Rudd stated: "I know how personally committed you have been to ensuring that the inquiry is a success for those at its heart: the survivors and the victims.
"You have consistently demonstrated your desire to leave no stone unturned in order that the voices of those victims might be heard.
"It is a testament to your commitment that you have taken the difficult decision to stand down now, having set the inquiry firmly on course, and allow someone else to lead it through to the end. With regret, I agree that this the right decision."
Her resignation comes after it was revealed that she had spent more than 70 days working abroad or on holiday during her time in charge.
An inquiry spokesman said she had spent 44 working days in New Zealand and Australia on inquiry business in the first financial year of the inquiry and that she is entitled to 30 days' annual leave.
The inquiry has been beset by delays and controversies since it was first announced by the then home secretary Theresa May.
Baroness Butler-Sloss stood down in July 2014 amid questions over the role played by her late brother, Lord Havers, who was attorney general in the 1980s.
Her replacement Dame Fiona Woolf resigned following a barrage of criticism over her "establishment links", most notably in relation to former home secretary Leon Brittan, who died in 2015.
Mrs May officially reconstituted the probe under Dame Lowell in March 2015 and placed it on a statutory footing, meaning it has the power to compel witnesses to give evidence.
The inquiry's terms of reference say that its purpose includes considering "the extent to which state and non-state institutions have failed in their duty of care to protect children from sexual abuse and exploitation".
It covers England and Wales.
There were high hopes for Dame Lowell Goddard when she became head of the independent inquiry into child sexual abuse last year.
Aged 66 at the time of taking on the role, in the spring of 2015, Justice Goddard was younger - albeit by months - than both her predecessors, Fiona Woolf, also 66 and Baroness Butler-Sloss, 81.
The new incumbent, as she was - a New Zealand High Court judge and mother-of-four - was described as "a highly respected member of the judiciary" at the forefront of criminal law and procedure in her home country for several years.
She was the first woman to be appointed to the Queen's Counsel, along with a colleague in 1988, and was also the first woman of Maori descent to have been appointed to the New Zealand High Court bench, in 1995.
She also helped establish police support networks for sexual abuse victims, and was chair of the Independent Police Conduct Authority report into police handling of child abuse cases.
In 2014, she was appointed Dame Companion of the New Zealand Order of Merit for services to law.
The Auckland-born judge is married with three step-children, as well as a daughter from her first marriage.
Her interests are listed as gardening, her family and equestrian sport.
The judge breeds and races horses, and supports various charities including Amnesty International, as well as those caring for animals and disabled children.
But her tenure was to last barely 18 months, and concluded amid revelations she had spent more than 70 days working abroad or on holiday in her first year in the role.