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SOIUSA code is the code used in the International Standardized Mountain Subdivision of the Alps (ISMSA or SOIUSA), a proposal by Italian Alpinist, Sergio Marazzi, to re-categorize the mountains and mountain ranges of the Alps. The proposal has been aired since 2005 but has yet to receive official recognition.

SOIUSA groups' hierarchy[edit]

SOIUSA pyramid showing its groups' hierarchy.

SOIUSA divides the Alps in two main regions, the Western Alps and Eastern Alps. These two main regions are further divided in:

  • 5 major sectors (SR);
  • 36 sections (SZ);
  • 132 subsections (STS);
  • 333 supergroups (SPG);
  • 870 groups (GR);
  • 1625 subgroups (STG).

Using this system, any Alpine mountain can be given a code which shows which region, sector, section, subsection, supergroup, group and subgroup it belongs to.


SOIUSA code is built in the following way:

  • 2 main parts:
  • 5 major sectors:
  • 36 sections: identified by numbers from 1 to 36 starting from Ligurian Alps and ending with Slovenian prealps;
  • 132 subsections: identified in their own section by the roman numerals needed to count every subsection;
  • 333 supergroups: identified in their own subsection by all the upper-case letters needed to count every supergroup;
  • 870 groups: identified in their own supergroup by all the numbers needed to count every group;
  • 1625 subgroups: identified in their own group by all the lower-case letters needed to count every subgroup.

Following these rules and using the punctuation marks (/; -; .; -; . and .) a summit will be encoded in the following way:

roman numeral (I or II) / upper-case letter (A, B or C) - number from 1 to 36 . roman numeral - upper-case letter . number . lower-case letter

In some case the final lower-case letter can be missing because some group is not divided into subgroups.
It can seldom happen (i.e.:Monte Tagliaferro) that a subgroup too is further divided in sectors; in that case the last lower-case letter is followed by a slash (/) and a second lower-case letter.

Encoding example[edit]

SOIUSA parameters of
pointe Sommeiller (Fr) /
punta Sommeiller (It)
  • main part = Western Alps
  • major sector = South Western Alps
  • section = Cottian Alps
  • subsection = Northern Cottian Alps
  • supergroup = chaîne Bernaude-Pierre Menue-Ambin (Fr) /
    catena Bernauda-Pierre Menue-Ambin (It)
  • group = groupe d'Ambin (Fr) /
    gruppo d'Ambin (It)
  • subgroup = crête Sommeiller-Vallonetto (Fr) / sottogruppo Sommeiller-Vallonetto (It)
  • code = I/A-4.III-B.6.b

Pointe Sommeiller (Fr) / Punta Sommeiller (It) code is:


It can be decoded in the following way:

  • I: the mountain belongs to Western Alps,
  • A: the mountain belongs to South Western Alps,
  • 4: the mountain belongs to Cottian Alps,
  • III: the mountain belongs to Northern Cottian Alps (which are the third out of three subsections belonging to Cottian Alps),
  • B: the mountain belongs to chaîne Bernaude-Pierre Menue-Ambin (Fr) / catena Bernauda-Pierre Menue-Ambin (It) (which is the second out of two supergroups belonging to Northern Cottian Alps),
  • 6: the mountain belongs to groupe d'Ambin (Fr) / gruppo d'Ambin (It) (which is the sixth out of six groups belonging to Bernaude-Pierre Menue-Ambin supergroup),
  • b: the mountain belongs to a subgroup called crête Sommeiller-Vallonetto (Fr) / sottogruppo Sommeiller-Vallonetto (It) (which is the second out of three subgroups belonging to Ambin group).


  • Marazzi, Sergio (2005). Atlante Orografico delle Alpi. SOIUSA (in Italian). Priuli & Verlucca. ISBN 978-88-8068-273-8.