Defense Secretary Philip Hammond is replacing Foreign Secretary William Hague, who announced his own resignation unexpectedly late Monday, and said he would not be standing for parliament again.
Michael Fallon, who first had a ministerial role under Margaret Thatcher in the 1980s, is to take on the defense portfolio.
Around a dozen men are leaving their ministerial posts, in what British media dubbed the "massacre of the men in suits" or a cull of the "male, stale and pale."
The opposition Labor party has in the past been able to attack Cameron for the lack of female faces on his front bench - until now there had been only three women in the cabinet, including Home Secretary Teresa May.
In the first of several high profile appointments, Minister for Women Nicky Morgan replaced Michael Gove as education secretary and education minister Liz Truss was given Owen Paterson's portfolio as environment secretary.
Esther McVey, a former breakfast television presenter, is to keep her portfolio as minister for employment and disabilities but will now also attend cabinet and is expected to continue as a prominent spokesperson for the government.
A former head of corporate affairs for the BBC, Baroness Stowell, was appointed as leader of the House of Lords, Britain's upper chamber, and so will also have a seat in cabinet.
The reshuffle is being seen as preparation for the general election in May, and is also setting a new tone for Britain's relations with
Europe.
SHI/SHI