Palazzo Margherita, or palazzo Piombino, is a palazzo on Via Veneto in Rome. It was built from 1886 to 1890 by Gaetano Koch for prince Rodolfo Boncompagni Ludovisi, prince of Piombino, on a now-vanished portion of the Villa Ludovisi. The high cost of the palace forced the prince to sell it to the Italian state.
The palace is named after queen Margherita of Savoy, who lived there after the assassination of her husband Umberto I in Monza in 1900, till her death in 1926. In 1931 it was acquired by the government of the USA and now houses the American embassy in Italy and as such is on America's Register of Culturally Significant Property.