New DUP leader Edwin Poots has begun assembling his ministerial team, nominating Paul Givan as First Minister of Northern Ireland's devolved government.
She has not spoken since Mr Givan's nomination, but will remain in post for a final engagement leading the British-Irish council in Fermanagh on Friday.
Once she has stepped down on Monday, the DUP and Sinn Fein will need to agree on who should be first minister and deputy first minister.
They will have seven days to come to an agreement or face the possibility of devolution collapsing and an early election.
Ms Foster was both DUP leader and first minister - but Mr Poots has said he prefers to split the role so he can focus on party matters.
He paid tribute to her "excellent work" as he revealed his new team at Stormont on Tuesday.
Accepting the role, which will begin on Monday, Mr Givan said: "There is a huge responsibility that comes with this position, particularly in serving the people of Northern Ireland."