It follows reports that President Trump was outraged by comments made by Mulvaney during the Ukraine corruption saga.
The allegations of abuse of power over the Ukraine incident led to impeachment proceedings against President Trump.
Mulvaney's departure has been on the cards for the last few weeks.
Mr Mulvaney is to become US special envoy to Northern Ireland, while North Carolina lawmaker Mark Meadows has been appointed to take over his former position.
Iran threatens painful response if US renews attacks
Iran said on Thursday it would respond with "long and painful strikes" on US positions if Washington renewed attacks and restated its claim to the Strait of Hormuz, complicating US plans for a coalition to reopen the waterway.
Ukrainian drones hit Russian port of Tuapse for the fourth time
A fresh Ukrainian drone strike on Russia’s Black Sea port of Tuapse, the fourth in the past week, sparked a fire at the sea terminal but caused no injuries, local officials said early on Friday.
Detained Myanmar ex-leader Suu Kyi to meet legal team this weekend
The legal team of Myanmar's Aung San Suu Kyi plans to meet the detained former leader this weekend after she was transferred to house arrest in the capital by the military-backed government, a representative said on Friday.
UK police charge man over stabbing attack in London
British police charged a 45-year-old man with two counts of attempted murder on Friday following an attack during which two men were stabbed in Golders Green, north London, in what officers have called a suspected terrorist incident.
His Highness Sheikh Mohammed bin Rashid Al Maktoum, Vice President and Prime Minister of the UAE and Ruler of Dubai, has praised the efforts of the first batch of Emirati government officials to secure scholarships to study at the world's top universities.
Dubai Police have summoned a driver for running a red light and trying to evade the authorities by removing the number plate of his Nissan Patrol.
The UAE's Attorney-General, Dr. Hamad Saif Al Shamsi, has ordered the referral of 13 defendants and six UAE-registered companies to the Abu Dhabi Federal Court of Appeal (State Security Court) on charges of illicit trafficking in military materiel, forgery and money laundering.
