Andrew Neill, The Spectator's chief executive, and Aidan Barclay, the chairman of the magazine's owner Press Holdings, are believed to have chosen D'Ancona ahead of Scotland on Sunday editor Iain Martin and The Economist's US editor John Micklethwait.
Neill described D'Ancona as one of Britain's foremost political commentators, and said: "He combines the requisite political gravitas and insight with the wit and originality that the post requires."
Deputy editor of the Sunday Telegraph since 1998, D'Ancona is also an author and novelist, a director of the Centre for Policy Studies thinktank and a member of the board of Index on Censorship.
D'Ancona described himself as fortunate to inherit a successful magazine from Boris Johnson, who resigned in December to pursue his political career as shadow spokesman for higher education.
"Under my editorship, I want The Spectator to adapt its fine traditions as a source of superb writing, news exclusives and wit to a new and exciting political landscape. It will be modern, free-thinking and indispensable."
The Spectator's circulation during the first half of 2005 stood at 67,120, up 5.4% year-on-year.
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