Properly Der Wiener Kreis, a group of philosophers working in Vienna in the 1920s who originated logical positivism.
Its leading members included: Moritz Schlick (1882-1936), Rudolf Carnap (1891-1970), Otto Neurath (1882-1945), Herbert Feigl (1902-1988), Kurt Godel (1906-1978), Friedrich Waismann (1896-1959); with Carl Gustav Hempel (1905-1997) and Hans Reichenbach (1891-1953) as associates in Berlin and Alfred Jules Ayer (1910-1989) in England, and Karl Raimund Popper (1902-1994) and Ludwig Wittgenstein (1889-1951) on its fringes.
The Circle was formally constituted as such in 1929, and dispersed after the German invasion of Austria in 1938, mainly to England and the USA. It published a journal called Erkenntnis.
V Kraft, The Vienna Circle (1969)