Cabinet member Simonetta Sommaruga of the Socialist Party took over the Swiss presidency on Wednesday, a largely ceremonial role that rotates between leading political parties.
The 59-year-old Sommaruga is the minister for environment, transport, energy and communication in Switzerland's seven member Federal Council, which is the executive branch in the wealthy Alpine nation.
She has sat on the council since 2010, previously holding the justice ministry post.
Sommaruga took over the presidency from Finance Minister Ueli Maurer of the right-wing Swiss People's Party (SVP).
Under Switzerland's so-called "magic formula" in place since 1959, cabinet positions are shared between the four largest parties: the SVP, the Socialists, the right-leaning Free Democratic Party (PLR) and centrist Christian Democrats.
The Green Party made historic gains at federal elections in October, prompting calls that it now deserved a Cabinet seat, but it has not yet managed to secure a place in the executive branch.