Motlanthe was sworn in and succeeds outgoing President Thabo Mbeki, who stepped down at the request of the ANC, CNN reported.
Motlanthe, who has roots in the country's labor movement, will serve as interim president until next year's general elections, scheduled for April.
Mbeki resigned Sunday amid claims of political interference in a corruption case against Jacob Zuma, the ANC leader expected to be elected president next year, the BBC reported. Mbeki denied the allegations, saying he was stepping down in the interest of party unity.
Notable deaths of 2014 [PHOTOS]