The previous worldwide improvement secretary turns into the primary girl to carry the place, and can proceed to function minister for ladies and equalities.
The appointment follows the dramatic resolution of the prime minister to sack Mr Williamson from authorities after she launched a leak inquiry to probe the disclosure of confidential data from a Nationwide Safety Assembly.
Former prisons minister Rory Stewart will substitute Ms Mordaunt as worldwide improvement secretary – the person accountable for overseeing Britain’s overseas support finances.
In an announcement, a Downing Road spokesman stated: “The prime minister has this night requested Gavin Williamson to go away the federal government, having misplaced confidence in his means to serve within the position of defence secretary and as a member of her cupboard.
“The Prime Minister’s resolution has been knowledgeable by his conduct surrounding an investigation into the circumstances of the unauthorised disclosure of data from a gathering of the Nationwide Safety Council.
“The Prime Minister thanks all members of the Nationwide Safety Council for his or her full cooperation and candour through the investigation and considers the matter closed.”