The Sylloge Nummorum Graecorum is a British Academy Research Project, the purpose of which is to publish illustrated catalogues of Greek coins in public and private collections in the British Isles. SNG has retained the traditional, very broad, definition of 'Greek' to include the coins produced by all ancient civilisations of the Mediterranean and neighbouring regions except Rome, though it does include the Roman Provincial series often known as 'Greek Imperials'.

The project was inaugurated in 1931 with the publication of the collection of Capt. E.G. Spencer-Churchill. A new and distinctive format was used, with text and illustrations on facing pages. This meant that only limited text was included, with the illustrations having greater prominence than in earlier types of catalogues, and to some extent replacing textual descriptions. This is because the primary purpose of SNG was to make much more material available for study. This format has been retained ever since and has been adopted, along with the title Sylloge Nummorum Graecorum, for similar projects in many other countries, including Denmark, France, Germany, Greece, Israel, Sweden, Switzerland and the United States.