On Her Majesty's Secret Service is the tenth novel in Ian Fleming's James Bond series, first published in the UK by Jonathan Cape on 1 April 1963. The initial and secondary print runs sold out, with over 60,000 books sold in the first month. Fleming wrote the book in Jamaica whilst the first film in the Eon Productions series of films, Dr. No, was being filmed nearby.
On Her Majesty's Secret Service is the second book in what is known as the "Blofeld trilogy", which begins with Thunderball and concluded with You Only Live Twice. The story centres on Bond's ongoing search to find Ernst Stavro Blofeld after the Thunderball incident; through contact with the College of Arms in London Bond finds Blofeld based in Switzerland. After meeting him and discovering his latest plans, Bond attacks the centre where he is based, although Blofeld escapes in the confusion. Bond meets and falls in love with Contessa Teresa "Tracy" di Vicenzo during the story. The pair marry at the end of the story but Blofeld kills Bond's wife hours after the ceremony.
Fleming made a number of revelations about Bond's character within the book, including showing an emotional side that was not present in the previous stories. In common with Fleming's other Bond stories, he used the names and places of people he knew or had heard of and Blofeld's research station on Piz Gloria was based on Schloss Mittersill, which the Nazis had turned into a research establishment examining the Asiatic races.
On Her Majesty's Secret Service received broadly good reviews in the British and American press. The novel was adapted to run as a three-part story in Playboy in 1963 and then as a daily comic strip in the Daily Express newspaper in 1964–1965. In 1969 the novel was adapted as the sixth film in the Eon Productions James Bond film series and was the only film to star George Lazenby as Bond. In 2014 On Her Majesty's Secret Service was adapted as a play on BBC Radio, starring Toby Stephens.