Nusach Ashkenaz is a style of Jewish religious service conducted by Ashkenazi Jews, originating from Central and Western Europe.
It is primarily a way to order and include prayers, and differs from Nusach Sefard (as used by the Hasidim), and still more from the Sephardic rite proper, in the placement and presence of certain prayers.
Nusach Ashkenaz may be subdivided into the German or Western branch ("Minhag Ashkenaz"), used in Western and Central Europe, and the Polish/Lithuanian or Eastern branch ("Minhag Polin"), used in Eastern Europe, the United States and by some Israeli Ashkenazim, particularly those who identify as "Lithuanian". There are a number of minor differences between the Israeli and American Ashkenazi practice, in that the Israeli practice follows some practices of the Vilna Gaon.
In strictness, the term "Minhag Ashkenaz" applied only to the usages of German Jews south and west of the Elbe, such as the community of Frankfurt am Main. North-Eastern German communities such as Hamburg regarded themselves as following "Minhag Polin", though their musical tradition and pronunciation of Hebrew, and some of the traditions about the prayers included, were more reminiscent of the western communities than of Poland proper.
The ritual of the United Kingdom ("Minhag Anglia") is based on that of Hamburg and presents the same hybrid character. See Singer's Siddur.
Leopold Zunz claimed that the Ashkenazi rite is descended from the ancient rite of Eretz Yisrael, while the Sephardi rite is descended from Babylonia. Haham Moses Gaster, in his introduction to the prayer book of the Spanish and Portuguese Jews, made exactly the opposite claim. To put the matter into perspective it must be emphasized that all Jewish liturgies in use in the world today are in substance Babylonian, with a small number of Palestinian usages surviving the process of standardization: in a list of differences preserved from the time of the Geonim, most of the usages recorded as Palestinian are now obsolete.