SOIUSA (an acronym for - English: International Standardized Mountain Subdivision of the Alps-ISMSA) is a classification system of the Alps from the geographic and toponomastic point of view. It was designed by , Italian researcher and author of the Orographic Atlas of the Alps SOIUSA. His book was presented with the patronage of the Italian Alpine Club on 23 Jan 2006, but has yet to receive any formal acceptance.
The SOIUSA is an interpretation by Marazzi of the terrain of the Alps aiming to replace the traditional way the Alps were partitioned in Italy, the , which was adopted in 1926 by the Italian National Geographic Committee () after the IX Italian Geographic Congress (). SOIUSA takes into account the European geographic literature normalizing and standardizing the different national classification systems in use. It was publicly presented in a lecture organized by the Italian Alpine Club's Milan conference on 6 April 2006, following the publication of Marazzi's book.
The SOIUSA introduces the bipartition of the Alpine System (Western Alps and Eastern Alps) replacing the old tripartite division (Western Alps, Central Alps and Eastern Alps) by a multilevel pyramidal hierarchy according to identical scales and rules.
Mountain groups higher level: fractionated with morphological and altimetric benchmark taking into account the historical and geographical regions in the Alps.
Mountain groups lower level: divided with a benchmark mountaineering.
Relative sectors (SR) intermediate to the groups above are also defined:
To any alpine mountain can be assigned a SOIUSA code, which shows to what part, sector, section, subsection, supergroup, group and subgroup the mountain belongs.
Example:
Names of higher level groups are given in the four main languages spoken in the Alps (German, French, Italian, Slovene) and in English, while lower level groups are just named in the language/languages of the concerned country/countries.
Examples:
From the line Savona - Bocchetta di Altare - Montezemolo - Mondovì to the line Rhine - Splügen Pass - Lake Como - Lake Lecco; they are divided in 14 sections (in brackets their highest summit).
From the line Rhine - Splügen Pass - Lake Como - Lake Lecco to the line Vienna-Sopron-Köszeg-Graz-Maribor and GodoviàPass; they are divided in 22 sections (in brackets their highest summit).