Germany's centre-left Social Democratic Party (SPD) has elected a new leader, the fourth in just over four years.
Mr Beck will be expected to turn around the party's fortunes
He is Kurt Beck, 57, the premier of the state of Rhineland-Palatinate.
Mr Beck, seen as a moderate, said after he was elected he would ensure the SPD was a force for social justice in the grand coalition government.
The party is currently in partnership with Chancellor Angela Merkel's Christian Democrats, which narrowly won last September's general election.
Mr Beck replaces Matthias Platzeck, who resigned on health grounds five months after becoming party leader.
Correspondents say Mr Beck faces a tough challenge to improve the SPD's political standing, which has waned in the face of Mrs Merkel's positive performance since the vote.