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.
Netanyahu says Israel to decide which international forces in Gaza acceptable
Israeli Prime Minister Benjamin Netanyahu said on Sunday Israel would determine which foreign forces it would allow as part of a planned international force in Gaza to help secure an end to its war under US President Donald Trump's plan.
Two suspects in Louvre jewel heist case arrested in Paris
Two suspects in the brazen daylight heist of some of France's crown jewels from the Louvre were arrested in Paris on Saturday evening and are being questioned, Le Parisien newspaper reported on Sunday, citing sources close to the investigation.
Russian attack on Kyiv kills three, injures 31
Ukraine's President Volodymyr Zelenskyy called for new strong sanctions against Russia and its allies after Russian drones killed three and injured 31, including six children, in an overnight air attack on Kyiv.
PKK announces withdrawal from Turkey
The outlawed Kurdistan Workers Party (PKK) said on Sunday it was withdrawing from Turkey as part of a disarmament process it is coordinating with the government, and pressed Ankara for concrete measures to move the process along.
Israeli military says it conducted 'targeted strike' in central Gaza
Israeli forces carried out a "targeted strike" on an individual in central Gaza who was planning to attack Israeli troops, Israel's military said on Saturday.
