Baron Leith of Fyvie, of Fyvie in the County of Aberdeen, was a title in the Peerage of the United Kingdom. It was created on 18 December 1905 for the steel magnate Alexander Forbes-Leith. Born Alexander Leith, he was the youngest son of Rear-Admiral John James Leith and his wife Margaret, daughter and heiress of Alexander Forbes, a descendant of Duncan Forbes, second son of the second Lord Forbes. He later assumed the additional surname of Forbes. Forbes-Leith acquired Fyvie Castle in Aberdeenshire in 1889 and invested large sums in its restoration. His only son, Percy Forbes-Leith, died while serving in the Second Boer War. Consequently, on Lord Leith of Fyvie's death on 14 November 1925 the barony became extinct.
However, his estates, including Fyvie Castle, passed to his daughter Hon. Ethel, wife of the former Conservative Member of Parliament Sir Charles Rosdew Burn, 1st Baronet. In 1925 the latter assumed the surname and arms of Forbes-Leith of Fyvie, for himself, his wife and son, according to the terms of his father-in-law's will (see Forbes-Leith of Fyvie Baronets of Jessfield for more information on the baronetcy). Fyvie Castle was in the hands of the family until 1984 when it was handed over to the National Trust.