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.
Israeli strike kills one in Gaza as sides trade blame for truce violations
An Israeli airstrike killed a Palestinian man in the Gaza Strip on Sunday, health authorities said, as Israel and Hamas traded blame for daily violations of a fragile truce that has largely halted two years of war.
UK police say mass stabbing on train not terrorist incident, two arrested
British police said on Sunday that a knife attack on a train which put 11 people in hospital was not a terrorist incident, adding that two men - both British nationals - had been arrested.
Israel urges Lebanon to disarm Hezbollah under ceasefire terms
Israeli Prime Minister Benjamin Netanyahu warned on Sunday that Hezbollah was seeking to rearm and that Israel would exercise its right to self-defence under last year's ceasefire accord if Lebanon failed to disarm the group.
Russian attacks on Ukraine kill two
Russian air attacks on Ukraine killed two people overnight and left tens of thousands more - and the entire eastern Donetsk region - without power, Ukrainian officials said on Sunday.
In line with the directives of His Highness Sheikh Mohammed bin Rashid Al Maktoum, Vice President, Prime Minister and Ruler of Dubai, the Mohammed bin Rashid Al Maktoum Global Initiatives (MBRGI) has announced the resumption of food aid deliveries worth AED43 million to the Gaza Strip,
Under the directives of His Highness Sheikh Khaled bin Mohamed bin Zayed Al Nahyan, Crown Prince of Abu Dhabi and Chairman of the Abu Dhabi Executive Council, Future Health – A Global Initiative by Abu Dhabi (Future Health) has been launched by the Department of Health – Abu Dhabi (DoH).
Toll gate operator Salik said it will charge peak-hour fees on Sunday, November 2, as the Dubai Fitness Challenge's first flagship event - Dubai Ride - gets underway.
