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.
No evidence alleged Bondi gunmen received military training in Philippines
There is no evidence indicating that the two suspects involved in the Bondi Beach attack received any form of military training while in the Philippines, the country's National Security Adviser said on Wednesday.
At least 12 killed in Nigeria mining site attack
At least 12 people were killed and three others abducted when gunmen attacked a mining site in Atoso village in Nigeria's restive Plateau state, a local group leader said on Wednesday.
Russian attack on Ukraine's central Cherkasy injures six, causes blackouts
Russia launched a "massive" drone attack on Ukraine's central Cherkasy region, injuring six people and triggering a blackout in part of Cherkasy city, the local governor said on Thursday.
UN, aid groups warn Gaza operations at risk from Israel impediments
The United Nations and aid groups have warned on Wednesday that humanitarian operations in the Palestinian territories, particularly Gaza, were at risk of collapse if Israel does not lift impediments that include a "vague, arbitrary, and highly politicised" registration process.
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